Slightly off the wall thought . . . based on an entirely different scenario, but just conceivably might be relevant here . . .
I have an Aeotec Z-Wave controller running on a Raspberry Pi - but if you plug it into the Raspberry Pi directly it won't work - you have to put an external USB hub between the two to get it to function.
The problem apparently is that the Aeotec device doesn't accurately follow the USB 3 power protocols - but the Raspberry Pi does - so when plugged direct, the Raspberry Pi correctly detects that something isn't doing what it should and shuts off the power - the external hub just supplies power pretty much regardless and everything works fine. So it is the Aeotec USB device that is at fault, not the Pi.
I'd also vaguely been aware for a while that some USB Ethernet adapters worked when PXE booting other (non-Geobook) laptops though some occasionally didn't, but never really thought about it much.
Is it possible that it is some of the USB Ethernet adapters that are actually the problem - and some laptops notice and fail to boot / recognise them - and some laptops don't care and let them work anyway?
I've no particular evidence one way or the other on this, but might it be worth investigating?