Heel-in vs Heel-out cleat disengagement on Speedplays

Hey everyone, I’m using Speedplay Zero Walkable cleats, and one thing that I noticed when I picked up some new cleat covers was that they instruct users to only disengage heel out, not heel in i.e. twist legs outwards instead of inwards to disengage.

As a habit, I’ve always disenagaged heel in rather than heel out. Does it actually make a difference on either the cleats or the covers, and does it have any physiological implications?

I don’t imagine it’s a huge thing, but got curious and thought to see if anyone might chime in, and decide if I should learn to disengage heel out instead of in.

I rode Speedplays for 12 years, zeros for probably 4 years of that. I never disengaged heel in. Huh. I can’t really see how it would affect things (on my Zeros, anyway… walkables might be different?) on the cleats themselves since they’re symmetric in engagement both on the cleat and the pedal.

I guess it never occurred to me to disengage heel in since that’s where my cranks, chain, chainrings, and other greasy stuff are, and there’s plenty of room to go out!