The rules for the Critical Hit deck back up the wording on p278. They say to draw a card, “whenever a PC scores a critical hit DUE TO A NATURAL 20 on the die roll.” The wording is the similar on the Critical Fumble deck too. There is no clause about, if the natural 20 would’ve resulted in a successful Strike or anything like that. “Regular” crits do not result in a card draw.
Taken together, Paizo seems to be saying that a natural 20 is always a crit. This suggests p445 needs to be fixed.
I’ve found this confusing since the first time I read the RCB, and I was surprised it was not clarified in the first round of errata. Its an important point that comes up a lot since its so much easier to crit now.