> Nothing prevents a vendor from implementing a high quality hardware encoder

Uh yes, it's called reality. Advanced video coding techniques are just too complex, full of serial and branch heavy algos to work in decently sized and priced ASIC or even in GPGPU. Which is the reason none exists outside of very expensive special stuff for professional render/streaming farms.

Not even mentioning that few coding tools are shared between codecs, so while you only need 1 CPU to handle all of them, you'd need almost an ASIC per codec...

If your claim is true, you won't have any trouble finding reputable tech publications saying that the video output from Apple M series hardware is substandard in some way.

I'll wait.

I would recommend you find a floor plan for Apple's M series chips and take a look at how big Apple's media engine is.