I really don't see the issue. If the work account uses Google or Microsoft I use their respective web apps and export an ICS link to see the blocked slots in my own personal calendar.
For my own personal calendar I use CalDAV, which is widely supported, and an app that can import ICS links. (Self-hosted Radicale server and the Calengoo app for mobile and desktop, for the curious.)
He's not suggesting to replace timestamps (nor database sequences). They're unique identifiers, and they happen to include a timestamp.