The Debian init system general resolution returns

... and PID 1 is never ever going to do _blocking_ send, regardless of the transport. Think what happens with the system where PID 1 is fast asleep... There's a damn good reason why systemd doesn't do blocking sendmsg(). The problem isn't transport one; it's that in congested situations you need to change the traffic you are generating. And sending the mount table updates is completely pointless, congested situation or not.