No, acoustically speaking, the instrument as offered by its maker cannot be further formed. It can only be deformed by dents. The lips, however, are adaptable and can learn. To form a tube, the instrument maker has a hydraulic press send a pressure of appr. 400 atmospheres through it. What is the human breath compared with such force? Nothing of course — but on the other hand our lips are extremely vulnerable. It is already surprising that someone should consider "forming" a metal instrument at all, but to think of "forming" a mouthpiece by one's breath or its motor is downright absurd.
Nobody can form the instrument or its mouthpiece by working them: one adapts oneself.
But why, will you say, get upset over those proud ones that think they can form and improve their instrument?
Because from a pedagogical point of view such notions are dangerous. A teacher, f.i., will dissuade a pupil from buying a good instrument under the pretext that he will deform it by his lack of experience, by his faulty way of blowing. The result: the poor pupil risks damaging his lungs having to play on some badly made or old instrument with leaking valves. The pupil will very soon get bored or deformed by the instrument. On the other hand it is easy to pretend that the instrument was badly formed to begin with and that it is not at all the pupil's fault if he does not make any progress (even on a good instrument) and that only buying another instrument could bring a change.