They put up 40+ points in each of those games. His "average" game during that 4 game stretch:

17-23 passing, 220 yds, 2 TDs, 1 INT, 11 rushes, 36 rush yds, 1 rush TD.

Also a comparison of defense strength that 4 game stretch came against (according to S&P+):

Stanford: 43rd in overall defense, 90th passing defense
Arizona: 74th in overall defense, 91st passing defense
USC: 34th in overall defense, 35th passing defense
UCLA: 97th in overall defense, 95th passing defense

Solid passing numbers against 1 solid defensive team and 3 pretty poor defensive teams last year. He performed well and did what you'd hope your QB would do against teams like that, but it's not like his performance in those games proves he's an elite QB or anything like that. I don't think he's anywhere near the "best QB in program history" hype he seems to be getting. Probably the best QB they've had since Brian Johnson, though.