"many PS5 APUs that didn’t meet console spec (“binned” or “defective” for console use) got repurposed. Instead of being discarded, these chips were re-used for mining/higher-density hardware."

Not discussed much in the article, but it looks like:

TSMC → AMD controlled/qualified the usable off-spec parts → AMD supplied BC-250 parts to ASRock → ASRock sold mining hardware.