> (Side note, doesn't 'zfs send' blindly trust TCP checksums?)

No.

https://openzfs.github.io/openzfs-docs/Basic%20Concepts/Data...

> End-to-end checksums are a key feature of ZFS and an important differentiator for ZFS over other RAID implementations and filesystems. Advantages of end-to-end checksums include:

> [...]

> - checksums on ZFS replication streams, zfs send and zfs receive, ensure the data received is not corrupted by intervening storage or transport mechanisms

Edit: Also, as Asmod4n points out in a sibling comment, neither zfs send nor zfs recv actually transmit or receive any data. They just generate a data stream that you are then responsible for handling somehow (piping to e.g. ssh, redirection to a file, etc).