Also a weightlifter (masters olympic weightlifting, nationally ranked). TRT and steroids are actually the opposite. Once you go off of them, your body starts to revert, muscle mass is lost, and often by more than you started with (because the body's natural production rates change with supplementation). It does take time, which is why sports regulatory bodies typically require specific time periods of hormonal therapy before they can participate, but their bodies will eventually adjust.
Sports regulatory bodies still test for hormonal PED, but their concerns have long swayed away from them because of the fact that they are so easy to detect and have the built in disadvantage of potentially altering your life negatively outside of sport. The current concerns have shifted to peptides and other forms of PEDs, because they are much harder to detect because they are 1) often naturally occurring but in smaller quantities, 2) don't actually directly act on the musculoskeletal system, but rather trigger natural processes that act on the system, and 3) often have half-lives dramatically shorter than most drug tests can even account for, and therefore require near continuous monitoring.