I think these are valid concerns for a project maintainer to think through for managing a chosen solution but I don't think there is a single correct solution. The "correct", or likely least bad, solution depends on the specific project and tools available.

For bug reports, always using issues for everything also requires you to evaluate how long an issue should exist before it is closed out if it can't be reproduced(if trying to keep a clean issue list). That could lead to discussion fragmentation if now new reports start coming in that need to be reported, but not just anyone can manage issue states, so a new one is created.

From a practical standpoint, they have 40 pages of open discussion in the project and 6 pages of open issues, so I get where they're coming from. The GH issue tracker is less than stellar.