HDRadio / Traffic Map

Can anyone explain how the HDRadio traffic map/reporting and fuel location work? Apparently, the two work together. However, their desperate operation doesn't make sense. Sometimes I get in my car and the traffic map/status are both immediately present. along with the fuel update. Most of time, I have to wait a 2-5 minutes and traffic comes up. Other times, its 15 minutes or longer. Note the fuel update is normally immediately present. In all cases, the HDRadio logo is showing on the traffic and fuel screens.

I'm trying to understand how/why the traffic information is not as readily present as fuel. Perhaps it is a larger information download. Do I actually need to be traveling on a road where traffic information is monitored for it to start working? The system obviously knows my location as the fuel report is immediately present.

I've asked the team at my local dealer about it and, frankly, they don't know. (No knock on them. This is a pretty small matter with respect to the vehicle.They are busy folks.)