They bring in Judo coaches too, are they training Judo 25% of the time?
Maybe they are doing 25% Judo, 25% Muay Thai, 25% Wrestling, 25% Boxing, 25% MMA, 25% BJJ. Anderson Silva also saw Steven Segal a couple of times, that's another 25% of whatever that guy does aside from eating.
The fact that you are referencing GSP meeting Freddie Roach highlights how much of an exception that really is, because that is from a long ass time ago.
I trained at a gym that is better than GSP's, and there are no coaches anywhere near the level of Freddie Roach there, much less regulars.
If you want to say they are using their hands 25%, then sure. You are right, most using your hands is the most common way MMA fighters engage. I'm just saying, that isn't really "boxing" (we are speaking English, so boxing means Western Boxing, IE the sport that Jake Paul participates in).