I suppose but if we're being fair then lets not forget that everything you mentioned there can be done in conjunction with Rationalism as well, which kind of fails to make a point as Rationalism is better producing science thus generating more of it faster. I'm not saying you can't win with Piety (I'm winning a cultural game with it right now), I'm just saying there's a reason everyone is taking Rationalism.
Yeah true. You really have to push your religious advantage and spam as many cities as possible to be able to surpass Rationalism in science.
However, I can see it working on maps with a lot of space for spamming cities. It's certainly much harder than pressing on a few policies in Rationalism though.
There is also the possibilty of one turn of anarchy and pick rationalism anyway when faith isn't as important anymore. But that's just a wild guess ^^