What I mostly do not understand is that Apple did not structure this as a 'we will store your library for you' instead of a 'you can redownload from the store a

What I mostly do not understand is that Apple did not structure this as a 'we will store your library for you' instead of a 'you can redownload from the store anytime'. The first case would mean that rights holders cannot force Apple to not redistribute that data anymore, because either it would be transparent to Apple, or at the very least the ownership for that copy of the data would lie with the customer, not with the rights holder. (And ofcourse it could be a nice implementation detail that Apple deduplicates multiple copies on their servers). The only conclusion to be drawn is that Apple does not care for the best interests of their customers, and probably gave in to the demands of rights holders, which is concerning.