I actually fixed a UR a couple of weeks ago where Waze was doing exactly that, preferring a MH where other route choices exist. User complained Waze kept trying to send them to a MH that was another 5-6 miles up the road when there were some mH and primary street alternatives that were a shorter, and depending on traffic, often faster. That was one of the instances I had mind when I said that the urban classification maps often over-classify a road segment when taking into consideration Waze’s routing temperament.
I also saw this, and corrected it, last year when making a trip from Memphis, TN to Gulf Shores, AL. Even when I got closer to the mH segment(US-45 Alt, which I upgraded to MH, as it should have been all along) it STILL wanted to force me over to the MHs which were a longer, and slower route to take. It looks like it took banished upgrading the last stretch of 2 lane US-45 between State Line and Mobile to MH to finally get Waze to route that way instead of trying to put you on a MH that was 15-20 miles further and a few minutes slower, just because it was a MH over a mH.
Waze’s over-preference towards highways of any type vs. roads that may make more practical sense is the only issue I really have with its routing style. I can understand why it can’t consider every possible route over a long distance, but perhaps it needs to be retrained to start considering lesser road types a little more either on short trips (less than 20 miles) or say within 20 miles of the destination.