If this Programmers SE question were asked on Project Management SE, would it be considered on-topic? If this question were asked here, should it be closed?
No, it shouldn't be closed. Dealing with clients is an important part of project management job. Even if we talk about small projects where there's no separate PM, it still belongs to the domain.
After all the question would require only a single tiny adjustment and you wouldn't guess whether it was asked by a developer or a PM.