I also did, and had written code for/on other mobile devices before, and did write a large number of even very ambitious software for other mobile devices later.

I do not see any past constructive experience as a waste of time.

Incredible counterexample, but oddly relatable. I'd probably have achieved techbro 'post-economic' status earlier if I focused on Android dev instead of the shiny (and new at that time) Xamarin for Windows phones.