The phrase "... must not begin with a hyphen" is duplicate since package names can already not begin with a hyphen or a plus sign. Reproducible: Always
There's nothing wrong with some extra redundancy. Here it improves readability.
As a native English speaker, given the audience for the document (technical people), I wouldn't waste their time giving them a rule then asking them to cross-reference it somewhere else and realise that it's redundant. That's just pointless.
