
I think so too and IIRC so were the 70's M's, but unfortunately I don't have any F's or M's to test. The later 80's made FF15 and VMS are "Variable Magnetic Shunt" which I guess is Ortofon's acronym for what's known as a moving iron.If I remember correctly, the earliest F cartridges were moving magnet as opposed to moving iron?
The one on the right in the left photo has a profile that's a combination of H and hour-glass. Many of the later and current styli are like this. I guess it's to allow the stylus to fit more than one type of VMS/F/FF cartridge body.
The "H" hourglass profile (a.k.a 'universal') is the later run of the FF15XE. It will fit where square "U" and "H" shafts will but not where solid hourglass profile do (top tier VMS bodies). The black FF15XE Mk-II, still available from Ortofon is likely sourced from Jico and is, or was until very recently, still made. Most of the Ortofon made styli in this series have a silvery sticker at the front of the cart while the later have the lettering printed directly on the plastic.To further add confusion the profile is different for same color stylus of same model.
The "H" hourglass profile (a.k.a 'universal') is the later run of the FF15XE. It will fit where square "U" and "H" shafts will but not where solid hourglass profile do (top tier VMS bodies). The black FF15XE Mk-II, still available from Ortofon is likely sourced from Jico and is, or was until very recently, still made. Most of the Ortofon made styli in this series have a silvery sticker at the front of the cart while the later have the lettering printed directly on the plastic.
Ortofon initially went through some length to make sure the lower tier bodies cannot be upgraded with the higher end styli, despite all the F/FF/VMS bodies being electrically identical. The universal profile is a regression from this policy.
I do believe the different shapes were Ortofon's way of controlling the cartridge upgrade path back then. Since today it is more about selling a replacement stylus, not an upgraded cartridge, the move to the universal fit is a good move.Ortofon initially went through some length to make sure the lower tier bodies cannot be upgraded with the higher end styli, despite all the F/FF/VMS bodies being electrically identical. The universal profile is a regression from this policy.

It's kinda silly b/c the bodies are all the same so the rating is strictly stylus related, but the top tier would be the VMS line up starting with the 3E all the way to VMS30. The FF15XE would be about the same in tracking ability as the 2nd in line 5E from the VMS series, except it's less of a compliant stylus so often better performs with mid/high mass tonearms. Excellent stylus. I love it too!