My rem chokes don't even have notches in them, they have the choke printed on the side, but the Beretta seem to be in line with what you have posted. Straight skeet choke doesn't have any notches at all, and I don't believe that they discern between sk1 and sk2 chokes. They can be had but I haven't seen them offered by Beretta.
IIRC the Ruger chokes also have the same notches but I would have to dig through a bunch of shooting bags to be sure.