I can't speak to Samuelsohn's policy, but I can tell you that I ordered a Samuelsohn suit from a store down here in DC in a model they don't usually carry. Measurements taken were accurate, but the model itself didn't match the description in the Samuelsohn catalogue, and the suit didn't fit properly. I politely but firmly pointed out the problems, and the store remade the suit at no cost to me.
As for Toronto - Harry Rosen has a mix of good and not so great salesmen and tailors. To get a good result, you need to find the right guy. Alternatively, wait for their Samuelsohn MTM event and there should be a rep from the company there to take measurements and give you some advice. You could even take in the other suit and show them what a disaster it is - the store you bought it from is doing no favors to Samuelsohn's reputation.
Another option for Samuelsohn is Theodore 1922 in the Annex. I bought a suit for a wedding from them in an emergency, and while they lean a bit towards the fashion-forward end of things, you should be able to guide them towards a more classic fit if you're clear with your requirements.