The term “command” commonly refers to the ifʿal form. But the existence of legal obligation is a broader issue than counting imperatives: a declarative form may impose a legal duty, and other valid evidence may establish a requirement.
Two questions should not be confused. First, which expression falls under the linguistic category of “amr”? Second, what evidence makes an act obligatory? A technical name for a speech-form is not the only possible mode of proof for a legal ruling.
For example, “fasting has been prescribed for you” is grammatically declarative yet imposes a sacred duty. Conversely, anyone can utter “do it,” but that does not automatically create an obligation under sacred law.
The distinction keeps the technical discussion of the imperative separate from all the avenues by which duties may be established.