Didn't know that they had an intake air filter, anyway not much needed IMO as long as you don't have 1 feet tall pile of dust behind, it will not be sucked....
Anyway I don't see what's wrong with this in that sense.....even in the most "clean-freak" owned homes it is common to have build up behind the dryer and or washer, as long as *nobody* usually move the appliances if not once every 2-3 months or more to clean behind them........that could only be considered a plus, not actually needed, but surely indeed helped giving the idea of it of something better.
Not a mistery that all other dryers until today as far as I know, didn't have filters  for intake nor needed them, it was not that much a revolutionary idea that actually made a difference...