It sounds as though you've done a ton of research on this, and how it will affect the marketplace, and Apple has done zero. Apple is just greedy and you're completely dispassionate and quoting the results of the extensive study that you have done.For most people, 16 GB is too little and 64 GB is overkill (especially now that music storage has become a thing of the past with MUSIC, Spotify and Tidal). You don't find it the least bit conspicuous that there's a gap in the middle? It's blatantly obvious that they want to force customers to go for an overkill model that wouldn't be nearly as popular if there was a 32 GB version available. The ones who would afford a 32 GB but feel that the 64 is simply too much will go for 16 and argue 'well, better this than no iPhone at all, guess I'll just have to sacrifice apps'. The fact that the 16 GB model lingers hurts both app sales and app evolution. Nobody wins, not even Apple - increased app sales would compensate for the nickels it costs them to stick 32 GB in the entry level model instead of 16.
But I still think it's the reverse. Apple has probably done the research and decided that the 16GB entry point, with a jump to 64GB is the one that is the winner for them.
If you actually do have research that says people who buy the entry level phone will buy enough apps to make up for the additional cost of putting 32GB in every entry level phone they make, then you should share it with Apple so they can fire the people who told them that entry-level phone buyers don't buy enough paid apps to make the upgrade worth the expense.