Ya'll taking this thing way too seriously. It's a curiosity for those who don't have the interest or money for a power meter. Like me
I mean you don't really do anything with watts if you're not going to train with them. However it's always nice to now your ballpark average fitness. Average speed is worth practically nothing if not done in a velodrome. The calculators you find on the internet are possibly as useful as this app but the good thing in the app is that you can access it mid ride and be surprised about how well you are doing.
It's for fun people! Don't you know that fun means?