I think Linus' point at the time was that the computational cost added to every transaction to protect against a (at the time) highly infeasible event of questi

I think Linus' point at the time was that the computational cost added to every transaction to protect against a (at the time) highly infeasible event of questionable impact was a poor cost vs. benefit argument. Adding complexity isn't free, and there needs to be a measurable benefit against a threat. But of course, now is not then. And I think zkms' metaphor "there's angry and armed people shooting at my plane with armour-piercing ammunition" is apt here. The threat is much more sizable now, and so the cost vs. benefit analysis has changed. Incidentally, one of the requirements of the SHA-3 competition was that it not be related to previous hashes. So while there are no demonstratable attacks against SHA-2, we nonetheless have "two ...hashes, and that they are based on totally different principles."