Most all are different animals. Why 500m? Because they had to pick a number? You could ask the same of any number then chose. 500m seems to be a nice even number. It's hardcoded so that DJI could appease the powers that be. Have no doubt... DJI and the various governments are talking and making compromises. Geo fencing has nothing to do with flying too high. The user can only over-ride areas that they should be able to fly within anyway... with no restrictions. DJI would not really be giving a person anything that they should not have been entitled to already.
@tcope i am in your neighborhood, rocky mountains just outside my doorstep
perhaps you have noticed that i have argued for "smarter" limits to replace the one size fits all "hardcoded" limits. i am not sure who the "powers that be" are, but the current magic numbers for the P3 are 500m ABOVE and 200m BELOW the take off point. rationale for these values is yet to be explained with any certainty. so, until we know, we can only agree that they are somewhat arbitrary and arcane. i'm sure they made some people feel good, though. i can shoot down the "safety" argument with some simple examples. i argue that a "smart" implementation was too complicated for what some developers could pull off in the short time that some attorneys wanted, so the compromise was a simple hardcoded implementation with some "reasonable" values.
i really have no intention of ever flying in anybody else's business, especially commercial airspace. if i could just fly over some hills/mountains that exceeded 1000m - while never flying above ground level by more than 50m - and descend into locations where I could capture some video of stock, feed, water, fences, etc - then i would be happy. however, this would require DJI to do any of 3 things: 1) increasing their hardcoded values carte blanche, 2) allowing end-users to exceed the limits but only after agreeing to certain terms and conditions (verifiable registration of drone, accept liability for whatever legal mumbo jumbo), 3) a truly smart implementation where current hardcoded limits are imposed, but (speaking of the height limit) if valid map datum is available to the app then the drone can travel within the limits AGL (above ground level) instead of above home point elevation.
#1 is simplest to developers, but may upset some attorneys/governments
#2 is relatively simple for developers and should be appeasing to attorneys/governments
#3 is really quite complex for developers and could not be argued by governments and would (hopefully) put some attorneys out of work
this is still oversimplifying a pretty complex problem, but i believe that if DJI can do what they are doing with no fly zones then they should be able to do this with other flight limits. at least start with the #2 solution while working toward #3
man, i can get long-winded. sorry.
(Utes or Cougs?)