S&W Cut vs Gunsmith cut.
I noticed this also. From what I gathered this referes to when the Gunsmith's just cut the back of the cylinder flat when converting one to moon clips. Like the way a 610 or 625 in 45 acp is done. The back of the cylinder is flat. No need for a raised edge to headspace the cartridge rim with loose rounds.
45 acp, 10mm & 40 S&W have no rim to head space on. The 45AR is designed to work in place of moon clip 45 acp, and is designed to head space correctly.
I think all the major shops are now leaving the cylinder outside edge raised on rimed cylinder conversions, so you can shoot them without moon clips. Clark did my 686 I am guessing over 15 years ago, and it is cut to shoot loose ammo.
I could be wrong, but I gathered this to be what was referenced.