I would hope that the "average UFC fighter" doesn't do silly things like "train lats" and instead focuses on "getting strong".
There is certainly not enough data to fairly answer your question:
1. AFAIK, no reputable survey companies are examining the weight training habits of UFC fighters.
2. For many fighters (and their coaches), actual training schedules are probably not going to be shared publicly, since training is your primary competitive advantage.
3. When fighters do "release" their training schedules, it's primarily a marketing thing, and most likely has no real relationship with how that fighter trains.