When I speak to folks about this topic, I frequently find that their definition of "gaining fat" and mine differ. For instance, if someone is happy staying at around 10% body fat levels then I could probably buy into the argument that folks think they aren't "gaining fat" when on trenbolone while still partaking in eating the occasional "dirty" food (by the way I absolutely despise the terms clean/dirty but we'll save this for another day).
I'm not someone who is going to be happy at 10% and so I'm going to notice when I start holding excess water and/or gaining fat a lot easier than these folks...
As you basically just described to me, you most likely aren't going to be above TDEE if you are eating three "clean" (uggh, grinding my teeth) meals along with one or two "dirty" (hitting my head on my desk) meals...
In other words, you aren't "eating whatever you want" or proving that it is "impossible to gain fat on trenbolone"...