Historically that's what I believe to be true.
This year I do think there's a chance that daytime crowds may be somewhat less on Grad Nite days versus non Grad Nite days because World of Color likely will not be playing to the public on Grad Nites, while a whole lot of people will likely want to visit DCA for World of Color, which will probably be playing on your non-Grad Nite nights.
Of course, if Grad Nites didn't affect daytime crowds last year, when everyone wanted to see the tweaks to Fantasmic, then it's possible that the same will hold true this year.
And if World of Color does make for incredibly large crowds, people who want to avoid crowds might choose Grad Nite days, making them crowded too. There's no way of knowing! I think there's a pretty good chance that WoC is going to make things a lot different than last year, though.