[tosti]

The map is woefully inaccurate, because it depicts present-day topology.

See e.g. https://upload.wikimedia.org/wikipedia/commons/c/ce/Peace_of...

From: https://commons.wikimedia.org/wiki/Atlas_of_European_history

[metiscus]

The map tiles themselves come from the Digital Atlas of the Roman Empire. Which you can find here.

https://imperium.ahlfeldt.se/

[tosti]

That's wrong, too. Seeing reclaimed land in there is a clear sign.