It doesn't take very much damage or deformation to a thread to make a very tight to almost impossible fit. Especially if that slight deformation is on the start of the thread and the other mating thread doesn't get aligned properly.

Also there are all sorts of fit standards for threads of the same pitch and diameter. So some parts with the same threading but different fit standards might be really tight depending on which is inside or outside thread.

It might be a stretch to assume every bicycle part manufacturer uses the same thread fit standard.