There is a minimum size required size for the file (cant be compressed beyond a few bytes - even if repeatedly applied) and the argument is only valid when we assume the files can be compressed to zero bytes.

no claim is made to the effect saying "Can be compressed indefinitely"

As I have told, the efficiency of it being able to compress over and over and over again may have chance for data corruption unless better checks and methods are added. (which will again increase the minimum required file size. but you can still compress it)