The ticket you purchased had no restrictions. In other words, it was an unrestricted fare which permits stopovers anywhere or that you can board anywhere on the itinerary. Of course, the other party, the airline, wants to maximize revenues so they will charge or tell the customer that they will charge someone the difference in fare.
This is completely unacceptable... how they get away with it it beyond me. Wouldn't the OP's friend be stopped in SYR for not boarding his YYZ-SYR segment? Or is this allowed since he was flying Full Fare Business Class?
Another suprising, (but good) thing is that I have always found fares ex USA MUCH cheaper than fares ex Canada, so maybe ex Canada is actually less in some cases
I guess this cannot be illegal then... otherwise these people would have been sued, no?
Cheers