Interesting approach. I can think of one more explanation the author didn't consider: what if software development time wasn't the bottleneck to what he analyzed? The chart for Google Play app submissions, for example, goes down because Google made it much more difficult to publish apps on their store in ways unrelated to software quality. In that case, it wouldn't matter whether AI tools could write a billion production-ready apps, because the limiting factor is Google's submission requirements.
There are other charts besides Google play. Particularly insightful id the steam chart as steam is already full of shovelware and, in my experience, many developers wish they were making games but the pay is bad.
GitHub repos is pretty interesting too but it could be that people just aren't committing this stuff. Showing zero increase is unexpected though.