My phone at least has a setting where I can choose what it does regarding a MAC address.
It can either use a randomised MAC address or it can use the MAC address of the router itself (can’t really see why you’d ever want to do that). So while I am sure traditionally the MAC address comes from the network card it’s clearly not the only way to derive one.
Also I’m almost positive that I went to change my graphics card and that changed my MAC address. It was years ago so I can’t remember the details but I remember it causing some problems with some work software until I realised that’s what had happend and just remapped the licence.