I got a very swift answer from their Lead Gunsmith yesterday:
"It's pretty simple. CZ made only 2 frame widths for all metal 75 series. 1.000" and 1.100", hence there are two different slide stops that cover these models.
P-01, 75D PCR, Shadow 2's, RAMI, Tac Sports, Shadow 2 Carry, etc, are 1.100" frames.
75B's, 97's, etc, are 1.000"
But when you select the 2ES Slide Stop on their online catalog it says it does not fit 75 pre-B.
However I just looked at the SS I did not want, the CGW Slide Stop for Narrow CZ Frame and it says it fits both B and pre-B... Doh!
I think it is safe, again, to blame the web witches for the misunderstanding...