So we have sources claiming there is a letter, and another source claiming there is not. Feel like some people would need to start going on the record before anything might reasonably be determined from this.
But in either case, I think Reuters absolutely had someone on the inside to leak this. They have made mistakes in the past, sure, but they are also not a tabloid and they don't innovate.
To me, a sensible conclusion of this is simply that OpenAI is not ready or willing to discuss this. Stuff that are supposed to be kept internal but due to the emotional state over at OpenAI, things might have leaked, potentially even out of spite.