What is exactly regarded as Magna Grecia? The site at Butrint used to be a part of geographical and cultural sequence of settlement in Ancient Greece. The same is true for Cyprus and Turkey. I would hence exclude the relevant sites in both countries. If the criterion is Greek sites outside of Modern Greece though, then Cypriotic Paphos and Turkic Troy for instance should be added.

I do agree with your first explanation: I meant to list Ancient Greek settlements / trading posts in (at that time) foreign lands. So Butrint has to go.