This is just not cricket from team Microsoft.
Per his writeup, he did not meet that person, which means that he most likely did not pass the interview.
He also for some reason didn't follow up on the results of the interview for 6 months, which is unique as most candidates will reach out. Assuming he actually filled out a job requisition, which he probably did to interview, he also should have gotten status from that requisition, so things are a little fishy.
I do not know anything about his case directly, but I would bet that he did not pass the interview and a decision was made to not bring him on as a result.
If Microsoft was trolling him to just pick his brain, they would have done more than two small events, and wouldn't have bothered to reach out to tell him they were releasing a product.
This response also burns any bridges that he had built with the team. He could have still potentially made something of his product if he had kept that relationship open and used his leverage as an existing package manager owner to influence WinGet.
If I was him, I would have at a minimum asked for feedback far earlier than wait for 6 months.
How exactly could a PM interview process (which is just asking you to walk through a bunch of design scenarios) give a stronger hiring signal than having developed a product the company wanted to acqui-hire? Honestly somewhat insulting that they made him go through a full external interview loop. At most it should have been some informal chats of the sort you get when transferring teams internally.
Wait, what? So if someone is a "name brand" celebrity, they should get to jump the queue and coast by with an "informal chat?" How is that fair? I don't care if I'm interviewing John Carmack, he's getting the same evaluation process I would give to any other senior candidate. Software Engineering's got enough problems with interviewing--it doesn't need an aristocracy that gets special treatment.