Either that salesman wanted to move an idle gun or has no experience firing either cartridge.
I recently tried to help out an older fellow in my LGS who owned a Taurus Judge and was told by the previous owner that he needed .45 "long" Colt. Only.
Period.
Probably should have minded my own business but I felt obliged (very respectfully, almost timidly) to point out the rather large stack of ".45 Colt" marked boxes were the same thing and the "Long" part was a misnomer.
They both looked at me like I had a lobster on my head and chastised me for not "staying in my lane" and, in fact, trying to put the customer in a dangerous situation because of something that I obviously had no idea what I was talking about.
Sad. Tried to do the right thing.
Next time I'll keep my mouth shut and MMOB.