Are socket ListenConfig Control hooks supposed to be skipped skipped under privilege separation?

[MegaManSec]

If username is not set, udpListenerFromAddr is called here which calls udpListenerConfig which calls net.ListenConfig{ Control: ... to set up a bunch of configs for the network. If userNAme is set, these configurations are not set here. Is this expected? How come we can't set dscp/tos, df/pmtud, buffer sizes, etc?