I'm speculating, but I bet if there's a place that has the numbers, you'd find very few programs that have the full 85.
Just from a theoretical/mathematical point of view, there are 11 players on offense and 11 on defense. In order to have a first, second, and third string for each position, that's 66 players. Your special teams are often mostly made up of offensive and defensive bench warmers, but even if you add another 11 players specifically for special teams (with special teams backups being comprised of second and third string offensive and defensive players), that's 77 players total.
Now, this doesn't take into account your "rotation" in the starting offense and defense for positions which will be involved with some plays but not others, such as receivers, running backs, defensive secondary positions, etc. But it also doesn't take into account that a lot of your third stringers/walk-ons (and maybe even some second stringers) are likely not on scholarship. Nor does it take into account the fact that not every position will be three players deep. And it overestimates the number of players you have that are solely for special teams.
So, yeah...without having actual numbers in front of me, I'd also have to agree that it's unlikely that most schools are using the max number of scholarships as it is.