And my experience is also only based on testing a handful of friends so might not be applicable to 100% of the population.

I think a more valid point to raise is that whilst the program says that riding on the drops compared to riding on the hoods might be worth 1 minute and 56.5 seconds, in reality the actual difference will depend on how high your handlebars are and how low you are when you get "on the drops"... everyone is different, but the program gives you a good idea of how much difference to expect.

Likewise the program says that aero rims might save you 34.5 seconds in an hour, whereas in reality some aero rims might make 40 seconds difference and others 30 seconds difference due to differences in the design of the two wheels.

So please don't think that the program is "exact". What it does do is give a quantitative indication of the relative differences compared to just someone on a forum or at the local club saying "this will make you much faster than that", etc etc.