stukey I beg to differ.
As mentioned in the referenced article, the EXO V3, which is backed by EXO REST API calls, is indeed out in general availability.
What Microsoft omits in all communication related to this subject is that the EXO REST API itself is still in beta.
So, we have general availability software (EXO V3) built on a beta API (EXO REST API). Not ideal, IMO.
It's in the interest of many application developers to use the REST API directly and not depend on EXO V3, which has to download itself every time you connect to Exchange Online (documented in the referenced article):
The performance (on frequent connections) is slow.
The temp directory gets bloated by downloaded modules if you don't disconnect explicitly from every session.
It would be nice to have an expected timeline and a change log for the EXO REST API.
(as is the case with, e.g., the Graph REST API: https://developer.microsoft.com/en-us/graph/changelog/
If I missed this information somehow, I'd be happy to receive a link.