In your brain, how much resources are being devoted to "fart noise improvements"? Do you imagine teams of people, endless days of meetings, strategy sessions, outside consultants, and government liaisons working on fart noises? It's a few people at most and it takes them a few days. It's probably the same people working on integrating Apple Music, they just took some down time and improved the fart noise system.
BTW - My friend's daughter, and my nephew LOVE the fart noises. Totally unimpressed with my car, but the moment my car farts, they light up. And now it's "UNCLE DEWG IS HERE!!! MAKE IT FART!!!!" I don't mind the little bit of time/effort it took to put in fart noises to watch those kids' faces light up.