Diagnoses are not about control, but more meeting the specific conditions, often which will contain requirements such as:
- The disturbance causes clinically significant distress or impairment in social, occupational, or other important areas of functioning.
- The disturbance is not attributable to the physiological effects of a substance (e.g., medication, alcohol) or another medical condition.
So forth. Diagnosis is about meeting all the criterion, not whether you control something or not.
DID is a shit sandwich, to be honest, because of exactly this. You intentionally change yourself, so one may argue you have DID, whilst another will say no. The same holds true for many psychologists who intentionally word questions towards people, and even train their clients, to use words like, alters, inner children, etc, to diagnose them with something that is actually more normal than not. People have many aspects to their personality, and psychology today seems to want to toss everyone with this normal trait into the DID or related basket if they present with trauma, just cause they can.
Psychology is a shit sandwich of best guesses. There is little evidence or science to validate any mental health diagnosis, so be super careful going into such areas with a professional, as you may just find something on your health record you don't want there, nor can you change.