Now that I watch the Clarke Cayman qualifying lap again, I don't see early apexing either
--at least not in most of the turns. Probably what I was noticing was his approach to T9/"The Off-Camber": it does seem like he hugs the inside curbing through here, but maybe that's where there's more grip. I do know that the late-apex/"safe" HPDE line through T9 has you stay out very wide to the right prior to initiating the turn due to the tricky mid-corner camber shift as the track rejoins the NASCAR straight, and also due to the very limited runoff on track-out. My most recent time at the Glen an instructor rode along and had me turn into 9 a lot earlier than the traditional HPDE/school line, and it worked well, but I was a bit apprehensive about it at first. Even that approach wasn't as tight or curb-hugging as Clarke's line in the video, though.
Again, though, not sure how I jumped from noticing this line through T9 to seeing "early apexing most turns."
I did notice on watching it again that Clarke has a bit of a wiggle and correction on entry to the downhill left-hand T6. I wonder if this was due to a bit of downhill trail-braking, which could make the back end come around as he describes in his turn-by-turn analysis on the linked website.