I just found out too after merging Plus and Team accounts.
Especially since I can no longer find some messages from my Plus account, which was actually the reason I wanted to export so I could search for them in the exported data - in case they were somehow displayed in the wrong order.
This is simply unacceptable. I may be wrong, but as I understand the law, at least in Europe, OpenAI would be obliged under the GDPR to provide a copy of the stored data in a “commonly used and machine-readable format”. It would be interesting to officially request the data copy based on Article 15 (3) GDPR in conjunction with Art. 20.
Irrespective of this, a corresponding notice when merging the accounts would be the very least that can be expected.
This means that the team accounts not only have advantages, but apparently also a considerable disadvantage or problem.