Right but if you have the forethought to go buy such a wallet, you could just make one yourself in advance and create a transaction history.

Although I would argue that even this doesn't have much value. It's not a big problem that people know "there exists an insider at OpenAI". There are plenty of employees there that shield you from being discovered.

In fact it would be so difficult to find this person among them, assuming the most basic opsec, that I'm highly skeptical they actually fired anyone. I would sooner assume this is just an announcement designed to discourage the behavior, since no specifics are provided.

You are giving a lot of credit to this criminal. I really doubt they thought about this long in advance of the crime. Are you suggesting they got hired at openai so they could make calculated wagers at Kalshi? This was more likely a crime made impulsively.