Good point, I was talking about similarly sized code bases, yes.
Because of the hefty CI runtime increase, myself I opposed to adding it. We have lots of parallel branches that people work on and many code reviews every day, where the CI just needs to run from a clean slate so to speak.
But most of the current long CI run penalty in the frontend of that comes from tsc, not ESLint, in my case.
I might look into it again.
In the project there already are all kinds of optimizations (caching to speed up full Ci runs with common isolated parts of a monorepo).
And for TS, project references + incremental builds for development are used, tsc in a monorepo would be miserable without them.