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.