Lets talk about this. The way the animation system is currently designed, an instance of an Animation represents the state of an animation for an individual element, so for reasoning purposes its easier to check for an individual element if an animation exists.

If a developer uses the animate service (eg, to build a popup component), most of the time they will probably want to only use the simple case and animate a single element since in most cases that's all they will actually have access too. If we remove the ___ToAll methods, an animate implementation has to manage the list of future merging individually, and anyone using the animate service will have to wrap their call in a list, which will result an extra handle object that does a Future.wait on a list of a single Future.

It might be possible to avoid the extra future, and possibly make the 'element' parameter dynamic (accept both a list and a single element), but it seemed more explicit to have two explicitly typed methods for an api a developer would use.