The expected behaviour is to have online repositories enabled
when the livecd is running; the trouble with runtime detection
relates to the asynchronous nature of network configuration,
connection might get probed just before it is brought up
(thus failing the test).

Systems having been installed-from-live don't misbehave this way
so left unmolested.

Runtime detection is still available via use/live/repo/online
but is definitely not the default mechanism.