The current Lothian tracking system, at least from my observation (I am happy to be corrected), continues to be the legacy system which was used for the old AVLs. My assumption is that it is not directly compatible with the new AVLs, so although it receives location data (from both AVL and radio), it doesn't receive anything else.
The solution to this, which was actually initially introduced to allow 291-294 and the 600s to track when they had no AVLs, is for a system to manually insert the remaining information itself. It relies on control to manually set each running board to the correct bus, using a spreadsheet I believe. The system then uses the location of the bus and the trip the bus should be on to get the next stop data. This comes with many issues like control setting the wrong bus, a bus being set late, no bus being set at all, etc. It is also unable to take into account delays meaning it reguarly changes to the next trip too early which can lead to bus information disappearing. This is also why the data is not 100% consistent with the bus stop screens which does receive information from the AVLs.
Edinburgh Council was supposed to update their bus tracker API to use the new system by the end of April, but that hasn't happened yet.