No but big ass luggable computers have used desktop PC parts back in the day, Google "Dolch lunchbox computer". If you wanted the absolute most cpu power in something like a portable workstation that would be transported from job site to job site you could probably do something with an expensive 170x170mm mini itx format board and a 140W tdp cpu.

Even a microatx is just way too awkward a shape for a laptop really. You don’t want a square motherboard in a laptop, you want a (rough) rectangle so there’s room for a large battery cell.