the terms do mean something and you can look at which civics you are running. A "hybrid" economy is NOT always the most efficient, not at all. Because you can only run 1 civic from each category at a given time, you cannot maximize the efficiency of all of your economic inputs at the same time.
Example - you are playing a financial leader and cottage spam almost every city. In this case, you want to run US/FS. You will have 1 GP farm and there isn't much point running specialists elsewhere, and no point in settling specialists, thus this is a CE
- you are playing a phi leader and have a small empire (6 cities) but with good land. The land is not good for cottages but it has lots of food and hammers. In this scenario you might build a wonder or two early game and get caste early, and start generating tons of GP. Now, this could go a few ways from here. You might bulb like mad and get a tech lead and then conquer the world with cannons and grens, without ever building a cottage - thus a SE. Or you might start settling all those GP in your capital and continue to develop and grab the occasional wonder, and then get constitution early and run REP. You never build a single cottage because you run REP, caste, and pacifism and use the slider to deal with emancipation penalties, again, no cottages, thus a SE.
To take up
Kadazzle's point, you're confusing efficiency as a matter of tile yields with efficiency as a means to secure victory.
Strictly speaking, the best tiles to work in the game are Towns that have been boosted by Universal Suffrage and Free Speech. As long as you can secure the Kremlin, their productive capacity exceeds that of Communist powered Workshops and Watermills.
However, on most maps, it is not "efficient" (in terms of winning) to wait until 1300-1600 AD to become "efficient" (in terms of tile yields). If you have an equal or smaller number of cities than any one AI, their bonuses, particularly at the higher levels, work in such a way as to prevent you from outpacing their tech or production rates.
Going to war with whipped Elephants vs. Archers is more "efficient" than working Hamlets and Villages because it secures you additional cities with additional infrastructure, tiles to work, and potential production. Drafting and whipping Rifles
en masse is more "efficient" than working Towns in Free Speech, because the unit is so much more powerful than defenders from the previous era.
That is why a hybrid economy is, as a rule, the most powerful. A hybrid economy denotes flexibility, and with a non-Financial leader, this usually means that the capital will be cottaged and serve as the driving force for your empire's beakers and gold. Other cities help to grow these cottages and produce infrastructure, units, and great people via less "efficient" farmed tiles. These tiles can then be converted into Workshops and Watermills at the time when new civics and technologies make these options more "efficient" (usually after or during a Renaissance war).
A Philosophical leader does not add much to a Specialist Economy. Running Specialists in six cities will not secure you one GP per city. A hybrid economy is still more "efficient," to use that word once again: one or two cities should run Specialists, which they generate at 100% speed compared to other leaders. One of these should have the Heroic Epic and, ideally, TGL. Other cities should still whip units/infrastructure and build Wealth or Research. Your capital should still be cottaged.
Obvious exceptions to the above are the SSE and an early Mids for Representation. You should also (and always) play the map.
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