It's certainly true that microservices can be set up in such a way that they're really a distributed monolith. But you don't have to be a large, mature company

It's certainly true that microservices can be set up in such a way that they're really a distributed monolith. But you don't have to be a large, mature company to apply microservice best practices. A foundational best practice of microservice development is that each service has a staging environment that uses the prod endpoint for every service it depends on, and this is where you run acceptance tests prior to release. This way the staging behavior before release aligns with the prod behavior after release. The week N release for microservice A won't have a dependency on a new feature in the week N release for microservice B, because the staging environment for microservice A (at release N) calls into the prod environment of microservice B (at release N-1), so the release-blocking tests wouldn't have passed. It is a common and critical antipattern to have a single staging environment across multiple services, where each service calls the staging environment of each other service. This is a disaster waiting to happen for just the reason you describe.