It's not like Apple desperately needs the PR and why risk bad one?
Perhaps what I should say is that orchestration seems like a plausible scenario to me. It seems to fit the facts and the outcome benefits both parties.
Remember when the iPhone debuted at $600 and no subsidy? People said it would never sell at that price. But of course a few did, and then Apple quickly cut the price to $400. Eventually it became $200+subsidy, just like any other smartphone.
Apple seems to start out with their preferred offer and see if it works. If not, they go to the next fallback position. That happens so quickly that it seems clear that they must anticipate it somewhat.
Apple has teams of people working through this stuff. So while you may be right that it was just a prepared backup plan, it also could've been the plan to begin with.
Regarding negativity risk. What risk? If you assume they planned this all along then how possibly this could be negative. The only risk they had if they would end up ignoring her.
This was a great PR stunt to make Apple look much better than a competitor and I'm afraid Swift was nothing more than a puppet there.
Do you really think that recording companies would allow Apple to just stream their music without any contracts in place? Or not including something so important as a part of it?
Why would she be so intent on getting involved with Apple's streaming service?