Sorry: your argument isn't very convincing. A "regular PC" has the ability to play XBox games, which MS designed into Windows 10 to be able to do. A more likely scenario: the XBox Series X includes a specially designed bios firmware, which is resistant to being re-programmed. Either by de-soldering, using a USB chip programmer & re-soldering the bios chip, would be one possible solution. Or simply re-programming the bios firmware "in place", could also be a possibility.
As far as comparison with "SFF units like ASRock deskmini": the GPU included with the XBox Series X appears to be much better than any such "regular mini PC" that doesn't accommodate a current model of discrete video card. The XBox Series X GPU (~12 teraflops) alone appears to be worth something like $350, compared with current AMD video cards.
If some crypto-mining software could be installed on the XBox Series X (alternate boot O.S., when not playing games), I imagine the return on investment time would be under 4 months, at current mining profitability (Bitcoin >$29,000).
I think you are confusing the locked down system (which Microsoft fully controls and will control going forward including disabling anything it would find online should hardware be 'abused' (from their perspective)) with ability to run x86 games on commodity X86 hardware ('Windows 10' example). PS5 is also x86, so what? Could you get a hardware piece, keep it disconnected from net, do some weird thing to it and make it run your fridge? May be, but why? The amount of time and effort involved (and time is money) does not worth it, IMHO. You will also have write (and maintain) your own drivers, etc.
Ultimately, if you are stating this is easy and simple - go ahead and show us how to do it
and the last thing here is the question of what is the value of your time. Is it is worthless (time spent has no monetary value) it is one thing, is your time is worth something than such DYI monsters make even less sense.
for me, I work a good tech job that pays enough to afford toys and tools. if I consult outside of that, it is also $150+ per hour. how many hours do I need to spend on this hack this, junk that, to take a console under warranty and turn it into some tinker toy that would not be warranted anymore, may stop working any second, and otherwise is barely above trash level in terms of usability and support? in that amount of time , if I need to, I rather work and buy whatever PC/upgrades/hardware I want/need without having to worry about any of those concerns.. i.e. if I want Mac mini , I just buy one.