Not at all, really. It’s measuring position reports uploaded to FlightAware which is, at best, only loosely correlated with density. The rate of uploaded position reports for an aircraft depends a lot on what the aircraft is doing.
Possibly the unique aircraft counts are closer to what you want - they count unique aircraft seen within each time bucket. But I suspect that you will need to go back to the raw data (or at least the json output) and analyze it yourself to get useful numbers for density.
ADS-B data is fairly tricky to measure because there are so many invisible variables. Aside from changes in the RF environment, you also get changes from the day of the week, weather affecting flight patterns, changes in flight schedules, airport/runway closures, a helicopter that happened to spend a lot of time loitering nearby, avionics testing of an aircraft on the ground, an aerial survey flight that happened to be mapping overhead on that day, etc etc.