This looks very solid as a house rule to me, and I would go as far as suggesting this should be a default: what do people think?
Many advances allow a PC to roll (other stat) instead of (usual stat) for a move. E.g. the Maestro D' can take "You call this hot?" to roll +their key stat (hot) instead of +cool when acting under fire.
This means some stats, such as cool in this case, get little use outside of custom moves, and can lead to a problem highlighting stats for advanced characters: Either highlight the key stat, and give out shovels of experience, or highlight something that might never be rolled. A parallel problem is when you really want someone to be Cool today, but they tell you "I roll hot for cool, so highlight that instead", as it means you can't incentivise them mechanically to do cool stuff if they're a player that responds to XP incentives.
Proposed solution: If stat (a) is highlighted, but stat (b) would be rolled for a move that usually uses stat (a), gain experience whenever stat (b) is rolled as a substitute for stat (a).