I think it's absurd to dismiss this as 'player exploits system, player gets GUI error, player's fault'. The player building a moderate number of high-level buildings such as Cathedrals is presumably intended, so even though people probably aren't meant to have 50 weapons manufactories, that's only one example of a problem that can be applied to a wider range of more common situations.
I don't see why ANYONE would want to have the full list of exactly where all those Cathedrals are, and even those players - if they exist - are going to be disappointed, because you can't even see all of them; the list goes off the screen.
I love how you've names your provinces so sentimentally, quoo
If a modder wanted to fix this, all they'd have to do would be to make it a triggered modifier.