Magma cubes and slimes climb vines (unlike any other mob)

Magma cubes and slimes climb everything climbable and die because of entity cramming if we have 25+ of them because they are no longer inside a vine block. Any other mob stays at the bottom and cubes do climb.
To reproduce:
Build a 1x3 chamber with walls around it
Place any type of vines inside
spawn size 0 cube inside