Uncertain that it enables encrypted send and receive. It very likely decrypts to get it into the send format, and then is reencrypted on the receive side. Those are separate file systems so it's not certain that they share, or even should share, the same encryption key.

Update: Ahh well it helps to whole article before posting. Both encrypted and decrypted send/receive are possible. But this also suggests multiple keys per pool, a key per file system I guess?