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.