But that was under the assumption these chats were private.
Is that a satirical comment meant to trigger people? Why on Earth would you assume what you assumed. We've been warning people for DECADES that:
1) Any of your data put on someone else's server (aka, "the Cloud") is no longer your data. You must assume it is being scanned, read, and used for the service provider's revenue, because it is.
2) If a service is free, then the service is not the product. You are, as is your data.
And for the last few years (at least):
1) Anything posted into an AI service is being donated to the AI service.
2) Any company code, data, structures, etc. posted into an AI service is no longer the sole property of the company; but is shared property between the company and the AI service. If it can be used against your company (competition, law enforcement, etc.) it will be.