Sort of; at medium scale you can blue/green your whole system out of the monorepo (even if its say 20 services) in k8s and flip the ingresses to cut over during release.

Of course k8s not required, you can do it in straight IaC etc (i.e deploy a whole parallel system and switch).

It's still "mixed fleet" in terms of any shared external resources (queues, db state, etc) but you can change service interfaces etc with impunity and not worry about compatibility / versioning between services.

Throwing temporary compute at the problem can save a lot of busywork and/or thinking about integration problems.

This stops being practical if you get _very_ big but at that point you presumably have more money and engineers to throw at the problem.

Yes. And if you structure your code to explicitly do this, it is a lot easier to reason about.