I once again went through all the basemaps and was not able to reproduce what you've captured. I even switched my locale to see if that made a difference (it doesn't). But I think I finally figured it out. I went to the now-deprecated raster tile basemaps and looked at Terrain with Labels. I was able to see a difference across the border:
So what this might indicate is that your organization is still using the deprecated basemaps, and you need to move up to the new vector tile basemaps. The raster ones are no longer updated, and you'll like the vector ones much better for many reasons.
To verify what you are using, right click on the basemap and choose properties, then look at the Source:
Look for the ID in the source string, and let me know what it is. That way we can confirm that what I think is happening is happening.
Your org admin can also confirm which are being used in the organization basemap settings. Organization > Settings > Map > Basemap Gallery
More info: https://www.esri.com/arcgis-blog/products/arcgis-online/announcements/reminder-raster-basemaps-moved...