formatOnBlur overloading format/parse original meaning

This API seems conceptually broken right now. With format & parse we have a nice parity:
- format maps a state value into a displayable value (happens during render)
- parse maps displayable value into a state value (happens in a callback)

formatOnBlur though prevents format from being called during render - which so far makes sense, but it calls format inside a callback. So the parity gets lost but this also makes parse weirdly unusable with this option - because it still also gets called inside a callback, so suddenly parse's and format's role is the same (?), they both write to state.

Not sure if the problem is recognizable from this vague description - if not please tell me so and I'll try explain it better.