Same answer here. The Honda CRV (mine was a 99) and 2007 Ford Edge did not show the miles towed.
My Manx dune buggy shows the mileage while towing though, but who really cares with a 1967 that the speedometer has rolled over several times by now. Who knows how many miles are on the engine or transmission?
There are companies that made dsiconnects for cable type speedometers, that disconnect the speedometer while towing.
There is also a couple of companies that have automatic transmission pumps, that turn on and use power from the RV to run that pump while towing.
Fred.