Why do you need a CAA/CLA? The common reason given is to have standing in an infringement dispute. But for that you just need some ownership, which you have. The reason for full ownership is to be able to relicense. That’s what I object to, and I don’t see why a project specific group with partial ownership like NodeBB needs that. What protections are you seeking?

To be clear though, the context was that you found your own work had included the work of others and THEN went out and sought their copyright assignment. This isn’t someone seeking contribution. I fail to see why they would agree to that.