Available evidence shows Callin did not publicly launch within a few weeks of May 22, 2021.

Multiple independent sources state that Callin publicly launched on iOS in early September 2021:

• TechCrunch reported that Callin, David Sacks’ “social podcasting” app, launched on iOS and announced its Series A funding on September 2, 2021.​(techcrunch.com)
• David Sacks’ own Medium post, “Meet Callin, the First Social Podcasting Platform,” dated September 2, 2021, explicitly says, “Today is the public launch of Callin” and that it is available in Apple’s App Store.​(medium.com)
• An app metadata tracker lists the Callin iOS app release date as August 31, 2021, with subsequent updates through 2023.​(appshunter.io)

From May 22, 2021 to August 31, 2021 is about 14 weeks, far beyond the ordinary meaning of “a few weeks” (typically on the order of 2–4 weeks). There is no evidence of an earlier public launch window in June 2021; instead, all public references point to late August/early September 2021 as the first App Store release and public launch.​(vcnewsdaily.com)

Given that the prediction (as normalized) was that Callin would be ready for public launch within a few weeks of May 22, 2021, and the actual public launch occurred roughly three months later, the prediction is best judged as wrong.