Don - I was always hoping the closed hot water loop would slow that process down some but you are probably correct in as soon as you start moving the hot water in the closed loop it would cool it down enough to turn on the hot water heater element.
To me this is alot different of pulling hot water out of the system which would be immediately replaced with cold water. The new cold water added to the hot water tank would most definitely cool down the hot water system requiring the heat elements to be turned on.
Even if that happens for me it still would be a big PLUS for the smaller amount of heat I would need...
I wouldn't have to idle the MH all night long to keep heat going haha...
Roy Ken