I think the point is that the standby timer (I have a 5026 like Roden) only works on timed recordings. It doesn't work on OTR or even if you just switch the unit out of standby.
According to the manual for the 5026 (Under GUI Operation):
" 'Auto Sleep' sets how long the DVD recorder is switched to 'standby' mode when no operation of the system is detected (eg recording, playback, timer record, or editing)."
This is obviously not the case with the 5026, as myself and Roden have discovered. I have so far found it only works with Timed and Copy operations.
If the 5005 is anything like the 5026 (and I see many of the Liteon units are similar - if not the same) then this is surely a bug.