Doesn't seem goofy to me. Many encoders work this way: there's more electrical 'positions' than there are detent positions. The OP wants to send a keyboard command as soon as the encoder moves off the detent.
This will be a little weird as usually you would expect that turning the knob part-way and then letting it drop back into the previous position won't have any effect on the output (it does a right-left command) but I can see how this might be useful in some situations.
Looking at the provided diagram, there's 4 electrical transitions between each detent.
Proposed solution: use the Encoder.h library. Only send the key-command when the previous position is divisible by 4. On startup, the encoder can be assumed to be in a detent and not halfway between, so starting the position counter at zero will work. Zero is divisible by 4.
Obviously decide which command to send depending if the current position is greater or less than the previous position.