(Hi, I’m one of the authors of the article at the root of this thread.)
Considering your hypothetical stateless microservice change in the same root module as stateful services, problems arise when _someone else_ has merged changes that concern the stateful services, leaving you little room to apply your changes individually.
It’s also worth remembering that, even if a stateless service and a stateful service are managed in the same root module, applying changes is absolutely not atomic. Applying tightly coupled changes to two services “at the same time” is likely to result in brief service interruptions, even if everything returns to normal as soon as the whole changeset is applied.
Considering your hypothetical stateless microservice change in the same root module as stateful services, problems arise when _someone else_ has merged changes that concern the stateful services, leaving you little room to apply your changes individually.
It’s also worth remembering that, even if a stateless service and a stateful service are managed in the same root module, applying changes is absolutely not atomic. Applying tightly coupled changes to two services “at the same time” is likely to result in brief service interruptions, even if everything returns to normal as soon as the whole changeset is applied.