Not pedantic at all.
Personally, I remember the original TV play very well, and thought it was excellent.
But I would not expect the average person to remember it, and it's fair to assume if you were to mention a film called The Firm to most people, they would indeed think of the Tom Cruise movie, which is more widely known.
Personally, the fact that talentless hack Nick Love directed this remake is enough to make me steer clear of this one.