I'm not impressed, it's an AI-generated apology. A quick skim of their code or commit history makes that obvious that this project's development methodology was clearly flawed, and only someone who turned their brain off would have advertised those results in the first place.
Running more type checkers isn't really about strictness. The main benefit to library maintainers is to make sure that their APIs are compatible with whatever tools their users run.
This wouldn't really be an issue for most other languages, but Python's typing ecosystem is uniquely fragmented, with only partial standardization between several popular tools.
GP's point is obvious: performance is immaterial to the discussion. Static code analysis is about preventing bugs. Therefore OP fails to make any sort of point, as it's a straw man argument.
Maintainer here: that's not the expected experience. If you're able to share details about the project & file an issue on our Github, we can try to reproduce it and figure out what's going on.
Pyright had 100% conformance until recently. There was a new PEP that was accepted which required some new conformance tests, which no type checker has added support for yet.