I saw your review before buying my dryers, it’s a good post 
Regarding the dry air input - yeah it is better to supply 10% RH air but this exhaust fan right here in the picture below does OK, the RH reading is constantly about 20%. The ambient RH at ambient temp is about 50% where I am, and when it gets sucked into the dryer and heated, it’s about 10-20%.
Graph for science - why RH % reduces when air is heated (the absolute humidity stays the same)
Dryers I’ve had without an exhaust fan had the RH stabilise around 40-45%, sometimes with visible condensation on the inside.