I've shucked WD MyBook drives, just a plain SATA inside. I guess that it's cheaper to have a stock drive and a cheap SATA-USB adaptor in a shell than do custom electronics. I've not heard of any that are otherwise, but I've only done a few. I suppose it's possible that they could solder them in or have custom electronics but I would have thought that rare. It's frequently discussed on Reddit too, so there's plenty of folk doing this.
The big ones with a separate power brick, I've not looked inside the smaller USB-powered ones. My interest was in the >8Gb desktop drives. I'd imagine they're the same deal, but hard to say from the outside. I did have a part of one at one point, a USB-to-SATA circuit board that was useful for adhoc connecting 2.5" drives, but I can't recall if that came from an prebuilt or an old BYOD enclosure.
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.
Ok. So I have a bunch them here, different sizes, both SSD and spinning rust. The big ones are all consumer grade drives with a little adapter board like you describe. The small ones are a mix of a single custom board with a USB connector and adapter board based ones. The tell tale is the outer dimension in the length, if the case is a little bit longer than a standard drive you have a very good chance of having one with an adapter board if it is the same or even smaller than the standard format then almost all of them are custom boards. The really nice ones have NVME guts in them that you can immediately repurpose.
I popped open a WD 'My Passport' drive, 4TB. It's exactly that - no SATA connection at all, only a USB on a custom board. I should have guessed this, it really is too short to have much in the way of other electronics. Thanks for confirming about the larger models, it's always good to know where we can source spares in an emergency. Top tip about NVMe - I would never have guessed this was an option.
