IME, smaller people tend to have more problems with the Z series pedals than taller people due to the need to lean the bike over slightly to swing a leg over and clip in their first foot. When the bike is leaned over, the pedal is at an angle, and the foot has to be at the same angle for the cleat to engage. This can be super frustrating if it isn't identified as an issue.
The taller/more long legged you are, the less this is a problem, so it tends to skew towards the female demo. As a result, I know many women who have stuck with the x series which is much less sensitive to angle of entry.
Again, IME, most folks can get past this once they know what's going on, just need to reinforce the need to step straight down on the pedal.
Same thing is somewhat true in release mode, btw. If foot isn't flat to pedal it can be much more difficult to unclip.
Fwiw, nice thing about figuring all this out is that it means very few people actually need the light action versions of the cleat/pedal when they address entry/exit mechanics.
Tech writer/support on this here site. FIST school instructor and certified bike fitter. Formerly at Diamondback Bikes, LeMond Fitness, FSA, TiCycles, etc.
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