It’s a good positive signal, but not a good negative one.

It would be convincing if it said “I’m qwen-2025-12-whatever”. I agree it’s not dispositive if it refuses or claims to be llama 3 say. Generally most models I talk to do not hallucinate future versions of themselves, in fact it can be quite difficult to get them to use recent model designations; they will often autocorrect to older models silently.