Interesting. I'm ignorant of the mechanics of tile acquisition by culture. I just have let it happen automatically in the past. So this costs culture points that could otherwise be accumulated towards SP?
Another "soft" bonus one shouldn't underestimate (you kind of mention it but I think it should be pointed out explicitly) is tile claiming. ICS will mean you won't have to spend a single culture point on tile grabbing in the inside of your empire because cities will fully occupy all land with their first ring of tiles.

However, if you are born with three other civs on your continent, this stat appears to be just the thing to do right after you exercise your four horses of the apocalypse. Planning to give it a try this evening.
Culture is the only civ IV victory that requires a minimum number of cities , thus making it the only kind of win you can't acheive at all in a OCC