Interesting point, d2h 4k has TOW tuners built-in ( you can check info diagnostic) currently one is enabled,
That is why we are able to record and see same channel, may be future software version allow recording one channel and viewing another channel .
Comming to standby recording, when recording sechduled it should auto power on and should star recording ( if I have written SW code I will write that way).
You test let us know about standby recording.