Originally this climb was just called 10+... Then it attracted Yosemite's leading talent (Kauk) and was purportedly 13b- "a full grade harder than anything in the valley at the time" Then Moffatt comes along and onsights it, believing it to be 13a (great account of this in his new book!) Patrick Edlinger is said to have casually onsighted after Moffat. It was also later soloed by Clune...Later yet the 12c grade was kicked around for a while...Fun history for a beautiful line.
I have no idea how this crack was originally thought to be 13b... perhaps finger stacks had yet to be invented or the newly invented Friends just didn't inspire the needed confidence... 12a seems more like it... excellent, obvious protection (with modern gear) makes for stress-free onsights/attempts:)
With that said, this line is one of the Gunks finest. If only it was longer than 1/3 a rope length, and legal to climb, it would still be sought out by climbers from near and far.