This was done on purpose, as currently there are some tricky internal issues which mean that even if you were able to keyframe these properties they wouldn't work at all.
Specifically, this node relies on RNA updates being performed to flush the properties you edit into an internal representation. However, due to the messy ways in which these calls are used for everything else (including forcing dependency updates), it is impossible to currently run these update calls without making Blender unusable for just about everything else.
Known limitation. Cannot be fixed easily, and won't be fixed anytime soon.