There may be no reason for time/lat/lon, and that is precisely why it “shall” be included. I’m just picturing the requirements for a DO-178-A or B compliant device including this stuff. No real good reason, just regulations.
If there’s requirements for superfluous data, then those requirements have to be implemented and tested, and space for them allocated in the transmission time schedule.
I don’t think they’re transmitting anything that they don’t have to.