See this, for example: https://groups.google.com/g/opensshunixdev/c/FVv_bK16ADM/m/R...
It boilds down to using a Linux-specific API, though it's really BSD that is lacking support for a standard (RFC 5014).
It would also seem to break address privacy (usually not much of a concern if you authenticate yourself via SSH anyway, but still, it leaks your Ethernet or Wi-Fi interface's MAC address in many older setups).
It would also seem to break address privacy (usually not much of a concern if you authenticate yourself via SSH anyway, but still, it leaks your Ethernet or Wi-Fi interface's MAC address in many older setups).