Exactly. And this wasn't the only occasion. Others like Wendy & Lisa complained that they felt they weren't given due credit for their contributions to Prince's work.
https://en.wikipedia.org/wiki/Wendy_&_Lisa#With_The_Revolution
Yet, no one questions Prince's genius and they shouldn't either. In music, songwriting, production there are always gray areas where you can debate if people who didn't get credit would have deserved it and if yes then what kind of credit and to what extent. To act like it only happened in MJ's case is a big deal of ignorance about music in general. It happens everywhere. "Money" by Pink Floyd is credited to Roger Waters alone when it was a band effort. There are still debates about who wrote what in the Beatles. Most songs are credited to Lennon-McCartney because that was an agreement between them to credit everything that way, but from time to time one of them came out and said "actually I wrote it alone" and then the other disputed it and there were debates. Things like that happen ALL THE TIME in popular music - well, not just popular music. In classical and jazz too there are many, many occasions where great composers (we are talking about people like Mozart) took ideas from others uncredited to incorporate in their work. James Brown and Miles Davis took ideas from their band mates without crediting them and so on. Happens ALL THE TIME. But let's just keep bashing MJ for things that many other greats do too. Let's put his producer role passive-agressively into quotation marks because he didn't aspire to be a one-man-band just to show off. Never mind that great producers like Quincy Jones weren't one-man-bands either and they relied heavily on others too.
I think, besides artistic self-expresion, MJ and Prince had very different goals which they both achieved and they did what they had to do to achieve what
their goal was. I feel Prince wanted to be seen as this this lonely genius who was doing everything on his own. I think that image was important to him. So he did what he had to do for that image. MJ's goal was to reach as many people as he could with his music, to be able to talk to people through national, racial, generational etc. boundaries, to create music that was universal and global. And he did what he had to do for that. Prince achieved his one-man-band image and praises for that from the press (although like MattyJam pointed out there is also myth in that image), but he did not achieve the universal and same global appeal as MJ did, his music didn't manage to break down barriers to the extent that MJ's did, his music wasn't that was able to cross racial, national or generational bounderies, not to the extent that MJ's did, his music wasn't as globally and universally loved as MJ's.
And before someone says it's just cheap commercialism, it isn't. I don't think MJ's aspiration for such things were out of commercialism. I don't think he cared much about money. I think it was the genuine desire to talk to as many people as he could and to touch as many people's lives with his music as he could. Is there an ego element to it? Possibly, but wanting to be seen as this one-man-band genius also has an ego element to it. BTW, MJ's aspiration to break down barriers also helped Prince a great deal IMO. 1999 was released before Thriller but initially it wasn't really a huge hit. It was when MJ's Thriller broke down barriers that people also started to pay attention to Prince. I also think Purple Rain's succes too was a bit driven by Thriller's succcess and that artificial rivalry the media created between them at the time. So in my view Prince actually owes MJ's aspirations to break down barriers a LOT.
And Prince too had aspirations for (for a lack of a better word) "commercial success" at certain times of his career but despite the efforts he never managed to achieve that the same way as MJ did. So once again, they were simply in their own lane: Prince could play almost all instruments on his record if he wanted, while MJ had a great sense of how to make music that was universal and that will speak to a great number of people all over the world, from all cultural backgrounds, not just a certain limited demographics. That doesn't mean his music was cheap or throwaway. In fact, the contrary. He created some of the most lasting music in pop history. Until this day he has several albums charting on the Billboard 200 every week, 20-30 year old albums, without any hype or anniversary. He is the most popular non-current artist on streaming sites. That's the very definition of music that lasts, that stands the test of time. Eventually music is for the people. It's the audience that will keep your name going.
MJ never claimed to be a one-man-band so I have no idea why he is being attacked for not being one. It's simply not true that MJ fans routinely brag about him doing everything alone in the studio. I have never seen such claims. So it seems to be a strawman argument by Psychoniff, just to be able to use that to bash MJ. It's Prince fans who brag about him being a one-man-band, so if you want to dissect such claims and whether they are actually true or not you should go to Prince.org and discuss that there with Prince fans.