I'm going to have to disagree with you here. Airdrop is basically the same thing as Android's Quick Share/Nearby Share, utilizing BT to find and pair devices, and then perform a direct wifi transfer of data. Android<->Android works no problem. iOS/MacOS<->iOS/MacOS no problem. Hell, I can even do this between Android devices and Windows/Linux machines. But Android<-/->iOS/MacOS - FOR NO GOOD REASON other than to keep them separate for capitalist reasons (doesn't matter what excuse you give it, brand differentiation, brand protection, walled-garden security - they're all excuses at the end of the day).
>There's only very limited interaction with the file system in iOS. This is by design.
In response to that, Apple can very easily extend the functionality over the API-layer to allow the sharing of, AT LEAST, photos and videos between Android and iOS/MacOS devices without having to worry so much about this issue. No need to give direct filesystem access.