SerializableReactiveProperty<> inspector fields cannot be animated by unity timeline or animation clips

[TigerLouck]

I'm working on a project that uses R3 in Unity 6 with the Unity timeline package. I'm attempting to use the timeline animator (which functions on the same mechanism as the animation clip system) to drive the state of a script via an int SerializableReactiveProperty, but the field is failing to keyframe (see the first image, keyed frames are highlighted red during record mode, although I did check a regular int and it didn't highlight but did key). Not all fields are or should be keyable, but I was expecting this to be.