The whole right zone is a bit odd, not just the rack/instrument part. This problem also is what makes that when you assign a MIDI track to an instrument track and you disable it, if you add a new instrument track, your MIDI is going to forget which instrument track was pointing to and you’re going to have to re-assign it everytime.
And they haven’t changed this behaviour in years (decades, a whole life?). I wish they change it soon, but I’m not very hopeful.
In fact, they have to redesign all the elements in the right zone, especially the rack related.