The pistol barrels have a different hole spacing for the foreend as well. T/C probably wants to avoid the question of whether you should have a Buttstock or pistol grip on board.
I bought a 16 1/4" 250 Savage barrel from T/Cs Custom Shop with the intention of being able to use it as both a rifle and Pistol barrel. But then reality set in. I would have had to have two different scopes and swap them back and forth depending on what I wanted to do with the gun that day. I like to put a scope on, sight it in and not mess with that set-up again so I have never used that barrel as a pistol. Sean