I suggest reviewing and comparing your status keys (PLN/CUR/CPL for projects, NEW/INP/CLS for issues).
When tying a converted project status to it's originating issue status, the system first looks for an identical status key. If it finds an issue status key that matches the project status key, that's what it uses. Because the keys aren't identical by default, the system then falls back on "equates with" logic. So because there is no default PLN key for issues, the system selects NEW as the next closest match.
The best solution I have found is to create custom issue statuses that match every project status. E.g., make an issue status called "PROJECT: Planning" with a key of PLN and Equates with New. Uncheck all the request type options (Bug/CO/Issue/Request) and lock the status. This effectively hides the status from the status dropdown menu on the request and a user can never manually select "PROJECT: Planning" - but the system can use that status. This status makes it more obvious to the requester that the request has been converted to a project, that the status is now controlled by that project, and enables filtering the request from reports where status should only be NEW.
For more details, you can reference this article and scroll down to "Synchronize the Status of the Resolvable Object with that of the Resolving Object."
Good luck!
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