Yes, it's a conjecture, but frankly I think it's a conjecture grounded in a fundamental misunderstanding of how addiction works. Addiction is not an act or a pretense. You're dwelling on the Watson question and totally ignoring the far more crucial reason why I think it's a bad conjecture. The Watson thing is a sidebar. Heck, the main reason Holmes wants Watson to stay is because he's afraid he can't resist his addiction without her. So of course
it's more about his addiction than it is about Watson. That's the point I'm really trying to make here: that trying to explain his display of addictive behavior as "really" being about something else -- anything
else -- is unrealistic, because the very nature of addiction is that it overrides other considerations.