Historically they did contain a map of physically unusable sectors particular to the physical platters in the drive, and I'd be surprised if they didn't now. So

Historically they did contain a map of physically unusable sectors particular to the physical platters in the drive, and I'd be surprised if they didn't now. So the consequence of a controller swap was making the assembly unstable because you were using a foreign sector map; usually it was still enough to recover as long as you weren't writing new data. But nowadays a drive controller is far more complex, e.g. it might implement transparent hardware AES encryption, in which case swapping the board loses the key. And I've no doubt there are many modern manufacturing-related tricks for yield that go into them as well, any of which might make a different set of platters than what was shipped unreadable.