I don't think it's narcissistic, but it's not necessarily just about supporting them. It's a maneuver/test/demonstration of where he stands with various employees. It gives him information and sends a signal about his standing with OpenAI staff.
So many key employees are defecting, this Tweet could be interpreted as his support of the people siding with him over the good of the company, which would be narcissistic if the board had a valid reason for their decision. But all that's speculative.