Say, we call animate method on node $el and we if a complete handler.

As it said in docs, complete is "a function to call once the animation is complete."

Thus, *in case there's no other animation currently running" , $el.is(':animated') in complete handler should return false. It, nevertheless returns true.

Not only this is wrong because of the agreement about complete function,

this also makes impossible to check whether other animations are running or not.

And this is needed not that rare.