I don't know , It may be related to bifurcation angle and the size of the vessel . I am beginning to think.
What's the big deal ? Both LAD and LCX are anatomically true side branches.
Its a foolish question . There is no side branch for Left main .
Its not forbidden to call LAD as a side branch. It all depends upon the Indication and Individual arterial ischemic burden*
No, Dominant LCX with large OMs can never be called as side branch.
LAD is always the main branch and LCX is always the side branch by default.