Reason is that the DVDR needs to do analogue to digital conversion to feed the Sky box to the TV as you have it connected.
If you were using SCART however it could do it with a bunch of relays or a fairly simple electronic switch. neither of which require much power (or no ant all with relays if they are wired correctly!).
Therefore the DVD can keep the SCART switching active even when it is in standby but more than likely powers down the A to D converter circuits in standby.
Two options. Plug a SCART from DVD to TV so you can keep RGB recording and pass on Sky to the TV when the DVD is off. Might mean having to manually select HDMI on the TV if you want to watch the DVD that way.
Or plug the Sky box direct to the TV and use the "VCR" SCART on the Sky box to feed the DVD for recording. You will lose RGB recording this way however.
As for upscaling. I would place money on the TV and DVD using the same chipset, or very close clones. Since they are both Panasonic, hardly any point them re-inventing the wheel and using two entirely different technologies in two different products to do the same job. Then again I supose anything is possible