Plenty of LW's make that big cut, not just 2 like you claim. If you want examples of muscular guys, look at Dos Anjos (195) or Paul Felder (185-190), to go with the other names I've already mentioned.
If he was dieting down before cutting weight, he would be changing his physique. Judging by a picture he tweeted yesterday, he looks noticeably thinner than when he was fighting (still very much in shape though) so he may already be doing that.
Hendricks cuts from much higher than 190-195 so I wouldn't be so quick to compare him to GSP. When he was getting ready to fight Lawler, Johny was 218. Johny said he wants to stay around 195 but it hasn't happened because he can't stick to his diet (just one reason why Mike Dolce no longer works with him).
GSP himself said he's around 187 so I would say that trumps whatever sources you have read. That also means that he would not be considered a large ww, that weight puts him about middle of the pack. This isn't anything new though, his camp has talked about going to 155 for at least 5 years.