If you really want to know, you could do this:
uplug 7-pin, leave the engine off, measure the voltage at the tow vehicle batteries (should be around 12.5v "ish")
then, with shore power connected at the RV, plug in the 7-pin and again measure volts at the tow vehicle batteries after about an hour
- if it's gone up or stayed the same, that's a good thing
- if it's dropped, it's still being drawn upon and is supplying the house circuit in the RV
But then you'd have to start turning on various circuits in the RV to see if you can alter the draw at the tow vehicle; how much can you consume from the inverter system prior to making the truck give up amperage versus gaining amp storage?
Wait ... that sweater is starting to come apart again ...
To answer you initial question at the start of this Wayne:
- if I am connected to shore power AND I'm only going to be in the site for a quick overnight (late arrival, early departure), then I will leave the 7-pin connected as a matter of convenience (not to mention safety in case I would forget to reconnect it in morning)
- if I am not connected to shore power, then the 7-pin gets pulled always