The name of the design to first occupy a slot will be the name applied to all designs applied to that slot unless game is reloaded.
This occurs in the player inventory, hotbar, shipyard computer, storage block, and the factories as well.
In my testing a direct swap was not necessary to reproduce, as i could place design "a" in all slots and the design "b" would be labeled as "a" for all slots where "a" occupied the slot first.
https://youtu.be/onfpztbRAvM