Not an approved connection for two reasons:
► although you seem to have no leaks, the manufacturer defintely specifies that coupling for use on a smooth pipe, not on threads.
► a coupling like that should not be in an inaccessible location. The drawback with it is that if you ever have to cable the drain, the head of the snake may poke through the rubber. You need to get rid of the male adapter, and use stainless steel banded flex, with two different ends, one for tubular, one for IPS.
A plumber would be able to install this without flexible couplings, but at a minimum, you should do it as I described.