I think it out basically like you do. The supply (# of potential ridings of a ride) is fixed, and the demand (the number of ppl that want to ride a ride) is the only thing that can change the average time waited...
However, I did like Shaden's argument, that because most guests, who used to be content to ride, say 5 rides a day standby, are now able to ride them in less time (3 FP and 2 standby)... do they then:
A) feel they've met their target # of rides and thus not ride more
or,
B) feel they have yet to spend their 5 hours riding rides and thus go ride a 6th ride.
I think it's a mix of both. Ppl don't need to ride as much as a commando, but if they get done with 5 rides in 3.5 hours instead of 5, they might go for a 6th. Given they were happy before doing 5 in the same time, but now that they do the 5 a little quicker, do they in fact take one more ride of something.
And if they do, does that actually increase the demand. For now they will wait in line for an additional ride, but does someone else in turn get to ride one less?
I think we are indeed seeing slightly higher waits overall... because ppl are riding some things quicker, thus setting their sights on one or two rides more than they used to. Meanwhile the commandos are not exactly going home early, they're waiting it out too, trying to get on just as many as before. (and coming up short, for sure).