My understanding is that Elon Musk, a physicist by education, is indeed an engineer and was very hands on in the engineering processes at SpaceX, so I'd assume he wasn't out of the technical loop that led to design decisions at Tesla.
Can you be considered an "ist" by having just a BS degree. That is, physicist, computer scientist, etc...
If no, what is the requirement? Masters or PhD?
At least that's my 2c - it's all just semantics, and as such there are many possible answers here :-)
Launching payloads to the ISS is good enough for me.
By law, no one can practise as a "professional engineer" in Canada or the United States without a licence. The BS is just one part of becoming a professional engineer.