Copilot app unification: where are personal-profile chats actually stored?

Microsoft is combining consumer Copilot app and M365 Copilot into a single app. Right now, the M365 Copilot app has a personal profile with its own chat history and settings, separate from the consumer Copilot app, so the two appear to be separate on the backend. The profile switcher looks like the one in other M365 apps.

When I asked Copilot itself, it said that all chats in the M365 Copilot app, including the personal profile, are stored in the employer/enterprise tenant because of “tenant boundary rules,” with full admin visibility into the content. That would be completely different from the clear separation in OneDrive, Teams, or Excel, and a serious concern if true. However, Microsoft’s support documentation for the unified app says personal (MSA) and work (Entra) data remain separate and don’t flow between them.

Can anyone confirm where personal-profile chats in the M365 Copilot app are stored, and whether an employer can see them? Thanks in advance!