In my view all physical track infrastructure should be placed in the route. Track marks and triggers are the exceptions as they can, if needed, go into session layers.
Some creators do place some track assets, such as signals, in sessions so that they can run a modern era session with LED light signals and an historic session with semaphore signals. That is not an option that would appeal to me because there would be a lot of other structural differences that you would also have to split between sessions. Some of my early experiments in doing this when layers were first introduced did not end well.
But that is my view and experiences.