“is” is meant for a one time animation and is 1 beat. If you use “is” for walking, it takes 1 beat for the animation to complete. Have you ever tried to make a character do an animation immediately after walking while doing an animation but your character goes idle for a split second before doing the next animation? This split second idle pause is due to the “is”. This is a bit hard to explain but let me give an example
If you do this:
@CHARACTER walks to spot and CHARACTER is walk_sad then CHARACTER is laugh
Right after walking to the spot, instead of going straight to the laugh animation, the character will stop, pause and be idle for a split second, then finally do the laugh animation. That’s because they’re still trying to finish up that 1 beat from walking because of the “is”. That’s why it’s best to always use “does it while” when walking. With “does it while” you dont get that awkward pause