I'd suggest basketball is the real risk here, although as a fellow mountain-biker I can say falling off with an outstretched arm can be an issue

Your tear might be old and what we see is what's been there for yrs now. I can't really say. We will see more and more surgical repairs of these in the future. In general Dr's a to lazy to bother as most people do fine without. That said I think that there is longitudinal evidence to suggest a disrupted AC.jt leads to earlier onset of arthritic changes in the shoulder joint.

As to your height and posture, suggest finding a tall girlfriend!