Musk does not have a PhD in "Battery Technology." He has two bachelor's degrees. One in economics, one in physics. Zero degrees in Engineering.

I'm an Electrical Engineer by degree, and a systems engineer (with some ChemE mixed in) in my career. The difference between engineering and physics can be vast. Depends on specialization.

The main point is that Musk never, ever worked as a physicist or an engineer. Dolph Lundgren holds bachelor's and master's degrees in Chemical Engineering. He was studying at MIT when he quit to start acting.

Would you call Lundgren an engineer? I wouldn't.