But, in my scenario specifically, they will be forced to by market forces (to some degree). Being less aggressive is a competitive advantage. In my scenario, the market is going to be flooded with competitors, some of whom are going to use that advantage. Even if some users still prefer the other advantages of proprietary Apple (as they do in reality), at least the users who care can switch and benefit.
> This would not be possible with licenses that allow Apple to keep everything proprietary
Sure, you can't clone Apple with literally "zero software investment". They will always have some proprietary parts. What I mean is that, in my scenario, they would have fewer proprietary rewrites (from GPL) and would use common permissive dependencies more often. Thus reducing the amount of proprietary code, and making their stack more uniform, "shallow", and easier to copy. Being easier to copy sounds like a downside that they'd like to avoid, but it's also cheaper, so a tradeoff comes into play.