That depends on the brand. The lower priced brands, yes, those can be SATA, the more vertically integrated companies also make custom PCBs that just have USB-C without any SATA interface exposed internally.
I have a old WD small one that's kinda faulty (plugged it in then put it down heavily, it's not been right since), I should pop it open just to see what's inside, but it's older than the USBC models so could easily have changed. In any case, I don't think AI is eating the stock of slow laptop HDDs, so I'm not sure there's any need to buy these just for shucking.