I assume if you built an EU version of an app with, for example, your own browser engine then you wouldn't make the other "International" version available. What would be the point?

If you already have an international version, why would you prevent EU users from installing it?

If you don't have an international audience, it wouldn't make sense to build two visions. But I imagine many apps want to target users outside the EU.

I don't know. What does "Be available on iOS in the European Union only" even mean?

Because you did work to localize it, do GDPR Compliance and stuff?