I've had a1 report back since this guide where it fixed their Steamdeck and on investigating it turned out to originally be a 64Gb that's been upgraded to a larger size Nvme drive so looks like you're on to something with what you've said.
I'm sure Valve said that very same thing and probably for this very reason. I only found out it was originally a 64Gb deck 'cos I managed to find a steam page/link that included and linked all the decks info to my user account. For the past 3-4...
Hmm... maybe it's because the original was a 64GB eMMC storage device? The 256GB and 512GB versions all used nvme storage so possibly some kind of flag is set in the bios somewhere about the presence of the eMMC was hanging around. IIRC eMMC is...
I brought an older LED version Steamdeck today on a whim for £100 which had black screen issues but the touchscreen would work and it'd display using a dock but when not hooked to a dock it was black screen. The thing is, I'd tried near enough...