That is NOT the only difference.
There are a number of other differences, too, including how the firing pin is retained, the style of sights used (and the dovetails, which are greatly different), and minor changes internally, especially the hammers). Most parts (except hammers) will interchange. Older models don't have the decocker variants available, now, either.
Nearly ALL of the older (pre-B) CZ-75s have tighter mag wells than the current production guns and the older guns will not accept most after-market mags, even the great Mec-Gars.
The pre-Bs work fine with older factory mags, with current factory 10-round mags (ideal for IDPA and Production), and some will work with new factory 15 and 16 round mags... but not all. Its a crap shoot.
I've had several pre-Bs and have had this problem with all of them.
The 75B guns can use any CZ mag and generally can use the "clone" mags, too. (You sometimes have to enlarge the top of the mag release notch on "clone" mags, as the CZ mag release is a hair higher in the grip than the releases on clones; otherwise the mags won't lock into place. They generally work fine with that modification.)