In practice, there is no longer a pytype team at Google [https://news.ycombinator.com/item?id=40171125], which I suspect is the real reason for the discontinuation.
Especially when, in my experience, each checker produces slightly different results on the same code, effectively creating its own slightly different language dialect with the associated fragmentation cost. In theory that cost could be avoided through more rigorous standardization efforts to ensure all the checkers work exactly the same way. But that would also reduce the benefit of writing a new type checker, since there would be less room to innovate or differentiate.
the current generation (mostly ty and pyrefly right now, though major props to pyright for being ahead of the curve) is moving towards fast, incremental type checking with LSP integration, and pytype was never going to get there. it's fundamentally a slow, batch-based type checker, which will catch a lot of errors in your project, but which will never be usable as an incremental type checker within your ide. add that to the fact that it had a different philosophy of type checking from most of the other major checkers and you had users facing the issue that their code would be checked one way by pyright in the ide, and then a subtly different way by pytype in the CI pipeline.
I loved my time working on pytype, and I would like to see some of its features added to pyrefly, but it has definitely been superseded by now.