I would say that porting Mathematica to the iPad would require them to be able to run the Mathematica engine on iPadOS. And with the strict rules Apple has around arbitrary code execution I would highly doubt that is going to happen.
That’s actually a misconception: Apple has allowed interpreted languages (e.g. Python, as in Pythonista) to tun on iOS/iPadOS for several years now. The Wolfram Language is definitely an interpreted language and therefore would not fall afoul of their rules.
Other people below are showing 6-8 GB on their systems, so it's lower than what I recall, but still higher than your figure I would normally bet. Are you only counting 1.6 once?
Regarding running the engine on iOS: Technically they do that now with their Wolfram Player App on the iOS. The calculations are done on the iPad and not sent to a server like the Wolfram Cloud app.
> Apps should be self-contained in their bundles, and may not read or write data outside the designated container area, nor may they download, install, or execute code which introduces or changes features or functionality of the app, including other apps.