Interference can shorten that range. Expect the 5.5 mile range to be the same as they would advertise battery life. No one is getting 40 minutes on the batteries in day-to-day usage. In the same way, the max distance most likely is what was found to be the case in pristine conditions.
Yesterday I was doing a job where I had power lines between me and the drone and it was less than 300 feet from me. This is the first time I've ever had it lose connection and start the return to home process (I was using a V1 Autel
Evo 2 pro). It quickly regained connection and I took back control. I've been doing this since 2016, but I also don't fly the drone past where I can see it.
Have you attempted to fly it in an area that is without wifi interference to see what range you get there as a test? Lastly, under Part 107 rules, you must be able to maintain visual line of sight with the drone- I just wanted to put that out there for whoever may come across this thread in the future.