This seems to have been going on for a while, Toms Hardware have articles on these cards going back a couple of years -

https://www.tomshardware.com/pc-components/gpus/chinese-work...

It looks like for a while this was a way to work around the US tech bans in China. And cards with this mod pre-applied seem to be on ebay for about $500, which is cheaper than used 3090s from what I can see.