And for the users. Given that it's fairly technical software, it's reasonable to expect that folks would search the issue queue before submitting an issue. If the issue queue was split across multiple sources, issues would exist in one system and not the other.

Sorry if you disagree, but giving clear instructions about how to report issues and limiting vectors is fair, logical, and incredibly common and a best practice.

If said casual user doesn't want to bother finding where to report issues (which a competent maintainer would surely document in the main README), there's also a fairly good chance it's not a big deal to begin with or that the explanation is vague/unactionable, at least from my personal experience.