I think I know why Microsoft has decided to stay behind Google Chrome's release cycle and it is actually pretty smart and good.
Let's discuss this everyone, I do hope that developer team or Microsoft employees correct me if I'm being wrong.
So I think Microsoft decided to release version 79 as the first stable channel for the new Edge insider browser, and to be intentionally behind Google Chrome's release cycle, so that Microsoft browser will be more stable than Google Chrome stable.
In case you're not aware, Microsoft marked version 79 to be the first release of stable channel for the new Edge insider browser due to release in 15 January 2020. while Google Chrome stable version 79 was released December 10 2019.
This gives Microsoft a 35 days gap where they can hold on and wait for more bug fixes to be released for each version of Chromium from Google before they include it in their own browser.
Because when Google releases their stable builds, they always release some other minor updates for it later, mostly minor bug fixes and such. Microsoft can wait for all of them to be released and include then in their version before stable release. Because Microsoft is dealing with lots of companies and enterprises so their Browser is more important and mission critical than others.
Another good thing and advantage that I can think of about this 35 days gap is that Microsoft is not exactly following Google's features and road map. Microsoft has a different road map for their exclusive features that we, the users, ask through feedbacks, so it doesn't really mean that Microsoft is behind Google Chrome in terms of available features and abilities.
I don't know how Edge team are handling security updates. I'm sure they don't just pass any feature to the Edge from Chromium source without review and considerations, because we've seen in in the past. but they should give priority to the security updates that are in Chromium and implement them as soon as possible