There is huge difference here and two separate issues:
1. Fixed calipers can fit larger pad. Whether you track vehicle or not is irrelevant. There is more friction surface on similarly sized rotor compared to sliding calipers. Also, pressure is more equal hence lesser possible for rotor to start vibrating. Contrary to popular opinion, fixed calipers are not necessarily best option on track. They provide, again, more friction surface, but cooling has to be perfectly executed.
2. Bigger issue with Tesla is choice of supplier. They didn’t go ATE, TMD, Akebono, they went Chinese route. Considering that Tesla obviously has issues providing appropriate brakes (Plaid) only conclusion is that they really don’t care.