Well ....... Yes and No
Yes, I have heard of mildew smell in dryers.
No, it does not make any sense. It should not be damp enough.
Except, since it is in fact happening, the mildew causing materials must be carrying over from the washer. That means the problem in the washer is much worse than assumed. Or, the dryer vent or vent line is partially plugged and needs to be cleaned out to allow the machine to work correctly.
In the past I have suggested that the washer get multiple shock treatments to clear it out. I also suggested multiple dryer loads with a large load of DRY towels or rags, run for as long as the timer allows and as hot as the settings allow, to get the machine up to as high a temperature as possible. This will dry out any nooks or crannies where the stuff could be caught. I would think that most of the mildew material will get loose and get blown out of the machine. Anything not knocked loose will most likely stick to the surface and not cause as much of a problem.
The example from above seems to indicate that the number of loads per week went down dramatically and caused the problem to surface in the washer. Apparently it carried over to the dryer.
Since no one has complained that these ideas have not worked in the past ...... I assume they work... ;-)