There is an update rolling out to offline Maps data available on Windows 10 Mobile. As per many tips received and on checking ourselves we could see the update available on our devices. The update takes the Maps data version to 188.8.131.52.
It is obviously not clear what is new in this update but usually such update bring improved Maps coverage, more accurate directions and even visual improvements in the way Map appears. We will keep you updated when we come to know more about the changelog.
For updating, go to Settings—>System–>Offline Maps and check for updates.