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.