The map should really only show london travelcard/oyster validity stations and anywhere beyond the line leading of the edge of the map with explanation. I guess placing the Berkshire (and Buckinghamshire) stations on there is a marketing idea to make a thing of it, to make it appear that something is happening. As I said, there is no benefit to either London or Reading showing this on the map. The Harry Beck theory works for a London tube map but for longer distances it only causes confusion. If tfl begin there own or take over a fast GWR▸ service would Bath and Bristol, for example, appear on the map in the same manner?
It’s consistent with the stations on other routes such as the GN, that are either outside the zones, or where only contactless fares are available. That horse had already bolted...
Paul