Unless someone has data for the latest Intel chips (i.e. sapphire rapids) showing the opposite I'm inclined to think this is a meme from 2016/7 that needs to go the way of the dodo.
It was largely wrong then, too. Cloudflare, who really kicked off a large amount of the fuss, had "Bronze" class Xeon chips, that weren't designed or marketed for what they were attempting to use them for. They were only ever intended for small business stuff. Not large scale high performance operations. Their performance downclock for AVX-512 is way, way higher on Bronze.
Actually, I stand corrected, after double checking, Cloudflare were using Silver. Entry level data centre chips, instead of small business chips. Still not the kind of chips you'd buy for high performance infrastructure, and not intended to be used for such.
Xeon Silver 4116s hit the market at $1,002.00. The Golds were $1,221.00. The performance differences are quite significant. For something that'll be in service for ~3-5 years, $200 is absolutely trivial by way of a per-chip increase. It's firmly in the "false economy" territory to be skimping on your chip costs. It's a bit more understandable in smaller businesses, but you just don't do it when you're operating at scale.
Also remember: at the scales that Cloudflare are purchasing at, they won't be paying RRP. They'll be getting tidy discounts.