I understand the rhetorical dodges here, but as both a career SRE and a student of CS, I don't see anything here which invalidates the theoretical asymptotic be

I understand the rhetorical dodges here, but as both a career SRE and a student of CS, I don't see anything here which invalidates the theoretical asymptotic behavior. All of the nuance added here is a complement, not a replacement, for traditional theory. It is certainly true that the number of elements needs to be quite high before the question is theoretically interesting. The author is right to point out that L2 cache is quite large. Today's GPUs are also quite large in onboard RAM and have integer ALUs, so even millions of elements are not a problem for a basic consumer-grade video card. (Yes, I know that that sounds stupid, but GPUs and now TPUs in the datacenter are a real thing, even if they're quite unfair!)