It's not so much an issue about discrepancies between Android and iOS, but partly an issue of infrastructure, partly an issue of scalability, and partly one of relationship building with Apple.
The first two are somewhat coupled because a major limitation of the current build infrastructure we have for iOS is that it must run on macOS. This juxtaposes our Android build infrastructure which runs on Linux and can easily be scaled up and down to support changing loads in App Inventor. Currently, we are configured to be able to run 168 simultaneous builds of Android apps. If the numbers reported by our rendezvous server can serve as a good baseline as to the distribution of Android vs iOS users of App Inventor, we expect we'd probably need about 25% of that capacity available for iOS builds, so roughly 42 builds. Let's call it 48 to make the math work better. Currently, we have enough to support 1/6th of that. So either we need to make the existing infrastructure 5 times faster or we need to scale up the hardware significantly (and Apple hardware is not cheap).
The last item of the equation is the relationship with Apple. Recall that App Inventor is primarily educational in its goals and that means being able to engage students and teachers in a way that ideally won't require them to pay the development licensing fee to be able to install their own creations. Whether we can make any headway on this or not remains to be seen but we also don't want to overstep here and squash an opportunity to make this more broadly accessible to people.
).