[hello_computer]

If they expose it, that ties them to a particular hash algo. Hash algos are as much art as science, and the opportunities for hardware acceleration vary from chip to chip, so maintaining the leeway to move from one algo to another is kind of important.

[ThatPlayer]

Also similarly is filesystem's transparent compression. The checksum should be on compressed blocks, to check everything without having to decompress them during a scrub.

You'd need to match compression settings on both ends. A different number of threads used will change the result too, would probably change depending on the hardware.

Would also apply to encryption. Probably shouldn't be using the same encryption key on different filesystems.

Or if you're using bcachefs with background compression, compression might not even happen till later.