What microservices easily provide in this scenario that is far harder to pull off with a monolith is that with microservices the service owners are able to roll out a dedicated service as a deliverable from that dialogue. Whether the new microservice implements a new version of the API or handles a single endpoint, the service owners can deploy the new service as an extension to their service instead of a modification, and thus can do whatever they wish to do with it without risking any impact on their service's stability.