they have no effect on ml-200 legs or any other mechanical leg. you can ram them and theyll do ram damage but the grinding damage doesnt happen. i dont know if its the same for battlewalker legs.
I noticed that too, I think they have to touch the ground to activate.
That’s because ML hitbox is broken, almost any contact melee can’t properly damage it
Also fun fact, until somewhere in 2021, ML-200 lower hitbox allowed you to phase through all your projectiles while stil protecting your weapon, so it was possible to use them as armor while making your weapons invulnerable to all damage until the legs are taken care of
but gerridas are the same thing. these hyenas cant even touch them. still not sure about the BWL though… havent tested those…
i made a build though that has 4 hyenas on the front just for sng and it looks like a lawn mower lol.
heck slap a few more onto it and you can just mow people down without them ever being able to get away… the funny thing is if your build has enough power you can just keep up the grinding on it.
i think it has to do with the hit box. they cant touch legs like ml-200 or gerridas but i dont know about BWL though. i dont have enough blueprint slots to try it out either.
huh… i never knew that.
still the wide hitbox of legs should be compensated with more hp cause you could shoot these things from space and not miss… heck you could aim in the opposite direction and still hit them! 
Basically every single leg is like that, their actual hitbox is improperly aligned with the visual model, they changed the IK for legs like 3 or so years ago so they visually are in the different spot, for melee this is bad