I would say most of it is definitely fat. I’m sitting on 25-27% BF right now, 6"2 in height. I didn’t completely shut out legs, occasionally i would do leg press & leg ext, but probably only did these like 2-4 times in a month. I checked my log, and i did 1 week of back squats back in OCT 2013, i did a rep PR back then which was 160 x 2 (in the comments section i said it felt really easy). Then after that i decided that my knee was playing up again so i stopped until now, which i lifted 220kg for a PR. So yeah, still pretty strange.
Only thing i can really think of is the BW increase and my Central Nervous System from all the strength training helped my Back Squat??