If your threat model includes "I don't trust Apple", then all discussion is moot. You could provide all the hardware killswitches you want. Apple could still design a way around them to get your data while the laptop is active.

Now, if you trust Apple, the T2 chip is perfectly secure for this use case. Apple claims this serves as a hardware disconnect baked into the silicon, in which case it is no different from a mechanical switch.

Finally, the whole argument about user control over various security features is interesting. I will say that Apple has, better than any other manufacturer, struck almost perfectly the balance between security and usability. Apple's software/hardware security does its job, does it well, and gets out of your way. Including 20 different hardware switches and 150 different security settings that mean nothing to the average user would not be in their design language.

It's all about your threat model. Perhaps yours is a bit too severe to use traditional consumer devices.