Although it’s not stated, you can close mount this fan (see picture) by removing the ring in the ceiling cover and install it to the motor assembly using three screws: Get two used for the rod and one extra in the hardware pack.
Totally safe in my opinion, but do it at your own risk.
I needed a small diameter fan and this fit the bill. I had some problems with the parts but the distributor gave an appropriate discount which covered the cost of the replacement part. It is working fine a covers a good area considering it is a small diameter fan.