The Win10 key is in Windows but the same key is used for all upgrades of each Win10 product (ie home and pro). So, the key that I have for my home install is exactly the same as everyone else's that have been done as an upgrade.
That is strange, don't sound right, to be honest.
i do know that a lot of OEM machines have Windows 8.1 products keys burnt into the UEFI, one of the reasons I will not buy buy a pre-built computer and also why if i got myself another laptop it will be without a OS.
Desktop machine now powered by windows 8.1 pro 64bit, no dreaded metro, laptop by Linux