I don't care if you call it a "grandstand PR move". It detracts from what Apple has actually done. It was not a valueless statement of ideals. It's an actual piece of functionality that millions of people will have built into their smartphones.
Stallman sits around hypothesising about vague 'open systems' that—when fleshed out—are completely impractical for the average user. This does very little. You can all sit around installing AOSP (or some other lesser-known open-source mobile operating system) and write your own ML-powered cookie bucketing engines and pretend that this is a viable alternative, and that Apple hasn't done something objectively pretty cool and great.
Thee fact is, the Stallman philosophy is absolutely meaningless to the vast majority of end-users, and they are incapable of doing anything with it. What Apple has done is something that will help end users. It's a selling point, they might win some people over with it, boo hoo, there's no such thing as ethical consumption under capitalism. It still means a whole lot.