I think this rename is important. It is much clearer when state names are adjectives (look at the docs for each state: they use the adjective version of the state names).
I suggest some further renames:
- backward -> backwards (with an ending s). When you talk about movement, it needs that ending s.
- pause -> paused (to make it an adjective).
- stop -> stopped (to make it an adjective).
This would be in line with GStreamer, for example: