This is a good place for a brief intro to statistical literacy. I don't fault the report per se because they're measuring what is possible to measure, and framing it in the best possible light since the entire point of this slide deck is a pitch to investors. But it's riddled with nonsense that mirrors the challenges of social science and causes of the replication crisis we bemoan in non-profit research but seem to blink zero eyes over when it's industrial research.
Is user retention an ergodic process? Clearly no. From economic first principles, we know elasticity of demand is going to depend upon substitutability and disposable income of the user base. Both of these can and do change over time. From empirical results elsewhere, we can simply look at products that have existed for more than a single year and observe that user retention rates in 1995 did not always match retention rates for the same product in 2002.
Here we get measurement of a single cohort that has actually reached 50 weeks. Are they representative of a typical cohort? We have no way to know. And again, fair, this is the best the company can possibly do. They can't create data that doesn't exist and they can't draw conclusions that have no hard evidence for or against. But you don't need to draw unwarranted conclusions, either. It's also 15% at 50 weeks retention in that first cohort, not 20% at 52 weeks. Does that mean those 15% of users will stick around forever? We have no idea. Sort of. We actually know for certain they won't because they're mortal and will die. Setting that aside, might they at least become lifelong users? I suppose it's possible, but even real-world friendships rarely last a lifetime. Will the next cohort at least still show 15% at 50 weeks? We yet again have no idea.