Everything in your post is just wrong, you have some weird bias since apparently you just don't like how they depicted Russia.
First of all, it makes no sense to compare Russia with Japan, even if you somehow prove that Japan>Russia, it only means that Japan>Russia. Japan might be God tier civ, and Russia still might be top 5 civ in the game.
Second, your first bold is nonsense, Lavra is clearly better since it doesn't take district spot (which you refuse to take into account). It also gets some free tiles, which is not amazing, but still probably worth at least thousand gold.
I don't get the part about islands and so on - that's Japan's UA, so if you want to talk about it, talk about Russia's UA too. Yes, Japan gets great adjacency bonuses, but Russia gets tons of free tiles worth thousands of gold. At this stage, we have absolutely no clue what is better.
Religion - you haven't play a single game, yet you know in bold that Japan has outdone Russia in acquiring religion and generating faith. I'd say we have to see, it seems pretty unlikely. As Russia, you can instantly have Holy Site with +5 adjacency, you only need to place it in tundra, which you are likely to get, and get Dance of the Aurora pantheon, which will most likely be available anytime - not to mention that you can have fastest pantheon with Russia if you want to. Yes, you will need to sacrifice growth for a time, but it can be helped in other ways (with your fast and strong religion, for example).
Finally, getting defense. There are two things on which you mainly spend money in first 50 or so turns - tiles and units. Since you won't be buying any tiles with Russia (or at least extremely less than any other civ), you'll be able to rush buy many more units. Again, I (unlike you) am not sure how it will work in comparison with cheaper Encampment, but saying that Japan will have much better defense is just silly.
EDIT: It is not that relevant, but I don't think you're right about Japan's adjacency. I seriously doubt that it actually stacks up, and they get +1.5 for each district. My guess is that it is +1 only. I might be wrong ofc.
So because I really dislike their approach to their depiction Russia, that means I can't point out the mechanical flaws of the civ? That because there is a bias, I must inherently be wrong?
Japan being better than Russia
is relevant though, considering that Japan trumps Russia in the only field Russia can really do moderately well in (religion; culture is another topic altogether).
I like how you outright claim that I
refuse to consider the lack of a district spot being taken up by Lavras. I'm fully aware of this - where Russia will be spamming Holy Sites to get their Great Prophet points and, consequently, focusing less on Food to build pop to actually utilize the Faith from tundra, Japan will be building additional districts - however limited - to build those adjacency bonuses, providing Faith of their own. The only edge I would give to Russia would be if they get a pantheon first, and that's assuming they work tundra tiles from turn 1 when they should be working farms on grassland. Speaking of which, Tundras aren't exactly great for building pop; Russia's tundra bias will keep them from good grassland tiles, where Japan's coastal bias will not. This grants Japan the edge in pop and, as such, utilizing every tile and district built in their territory, at least before Russia can.
Considering one city's Lavra will grant only one tile per GP, that's either about 150 average if it's tiles from expending the unit, or 500 on average if it's tiles from expending a charge. Neither are bad, but necessarily good either; I'm more appreciative the Gold the UA will save.
Speaking of which - the Russian UA will save Gold over time, true, but will it be enough to provide a civ with proper defense? Especially a wide civ, which will put more of a strain on your treasury. Plus you'll be wanting to spend that Gold on GP when your Faith isn't enough.
Japan, meanwhile, has literally
direct combat bonuses thanks to Hojo's ability, plus the quicker acquisition of Encampments means you're at least guaranteed some raw form of defense. Russia is more up in the air - it's up to how the saved gold gets spent and acquired.
Where does that +5 adjacency come from, hm? Holy Sites get adjacencies from forests and districts (+0.5), mountains (+1), and natural wonders (+2). The only thing close to a guarantee from that is forests, as tundra tend to have those - and even then, at best that's assuming an all-tundra terrain with all forests surrounding the Lavra. That would give +3 Faith from six surrounding tiles in the best case scenario, whereas Japan can guarantee +3 Faith in their Holy Sites for every
two adjacent districts, with no need for the best case scenario from terrain. Meanwhile, an all tundra region would severely hinder growth in Russia's city and thus less pop to work the tundra in order to generate Faith, whereas Japan is far less likely to be in such a position and can get a steady pop.
On Dance of the Aurora, that will undoubtedly boost Russia's Faith output for sure. But where Russia will have to spend time founding cities, spamming Lavras, fighting defensive early game wars, and slowly getting citizens in their cities, Japan can secure itself with its direct defensive bonuses and better starting terrain, building up their religion over time and setting up proper infrastructure that will later be boosted even further with the Electronics Factory.
As for the possible incorrect stats for Japan: I think there's gameplay out there of Japan so it would be worth checking to see if district adjacency is boosted at all.
