Hello Dr Deb,
I have recently been to an interesting seminar with a saddle maker and fitter (of English saddles). He talked about how a majority of horses have a shorter right front limb, and in particular the humerus, which leads to an anatomical asymmetry in shoulder size and shape which needs to be taken into account when fitting saddles. His suggestion is that when the horse is standing square on a level surface, the left shoulder will be bulkier and the right flatter.
I do also recall a farrier some years ago suggesting that some horses have anatomical short legs, though I don't recall if he found this to be predominently on the right.
I wonder what your thoughts are on the presence of these anatomical short legs? If you have found that they are present, which bone in the limb have you found to be the major contributor?
And by the way -- how in the name of all good sense could it POSSIBLY be the humerus? You do, you do, you do need to consider the source. Do they really know any anatomy at all????? Commercial people can say anything whatsoever. Cheers -- Dr. Deb