Would be worth explaining why: my understanding is that if you sign a CLA, you typically give a right to relicence to the beneficiary of the CLA. So you say "it is a GPL project, my contribution is GPL, but I allow you to relicence my contribution as you see fit".
If the project uses a permissive licence already, honestly I don't really see a big impact with signing a CLA: anyone can just take the codebase and go proprietary with it. However, if it is a copyleft licence, then signing a CLA means that the beneficiary of the CLA doesn't play by the same rules and can go proprietary with the contributions!
If you don't want a rug pull, you should use a copyleft licence and not sign a CLA: nobody can make Linux proprietary because the copyright is shared between so many people.
If you use a permissive licence, then a rug pull is part of the deal.