Precisely. Mobile chips on standard boards are almost always proprietary/ one-off designs, which kinds sucks if you want to do anything custom with them or OC. Often times the fan won't even be standard or itll be like a thin 60mm one, so forget about things like RGB fans or using a standard -thickness 60mm unless you have a huge collection of metric bolts (I do and I'm still stuck sometimes) to use in place of the bolts for the thin fan.
I remember, only Once (I think), someone made an embedded/soldered movle chip on an regular board that was mounted at the correct height and used standard cpu mounting holes. Once. And that was a delidded chip raised to the height where a heatspreader would normally be for a regular cpu. Scary to mount, you sure as heck don't want to over -tighten the cooler, but it did work, and worked well. Was much cooler than any laptop or one-off heatsink, and I think that was just with an old Arctic $40-50 heatsink.
So yeah, if a mobo makers would give us that, or add a custom heatspeader to emulated the regular height and position of a reg cpu, I'd be one happy builder! I'm pretty certain I'd buy at least 2-3 such boards right away (if they're not to expensive) because I know of a couple friends that would probably want one, and I'd for sure want at least one too haha