Ah, that makes sense. Are the keys in title.keys specific to the instance of the game you bought or is there one key (that you could get from a website/torrent/etc) that works for all copies of a particular game?
I'm asking because if you'd have to buy the game anyway, then I don't see how Nintendo would even have a revenue loss from the emulator. If there is no revenue loss, then the decision seems to be solely about control.
prod.keys which is universally used by the switch consoles(one file for multiple devices)
title.keys which contains specific keys required by games(one file for one game)