If I stripped my old laptop down to a single PCB, it certainly wouldn't boot, it would be missing RAM, and storage. My PCs would have no RAM, no CPU, no storage, potentially no GPU, and most of the servers would be the same. The IPMI/iDRAC etc would boot up I guess if we count that, and we'd potentially get into the BIOS if a device has soldered RAM, but M.2/SATA attached storage or something?
We could debate about strict definitions all day, but I think the vast majority of people differentiate between a Raspberry Pi 5 (not a great example given it needs storage, pick anything with eMMC if you truly want everything on a single board) running a full Debian-based OS, and a Pico running MicroPython (or whatever your poison of choice is) and one task at a time, at least I do when it comes to this kind of thing!
We could debate about strict definitions all day, but I think the vast majority of people differentiate between a Raspberry Pi 5 (not a great example given it needs storage, pick anything with eMMC if you truly want everything on a single board) running a full Debian-based OS, and a Pico running MicroPython (or whatever your poison of choice is) and one task at a time, at least I do when it comes to this kind of thing!