This name change is about a single "app" that was formerly called "Office app", not to be confused with the Office "suite", which in more cases than not also gets renamed, but in a subordinate brand sort of way ("the Office suite of applications, brought to you as a part of Microsoft 365").
The "Office app" itself was mostly just a launcher for the other apps. Now it is also/primarily an LLM chat interface.
The "Office app" itself was mostly just a launcher for the other apps. Now it is also/primarily an LLM chat interface.