During a presentation given by Senior Webmaster Trends Analyst John Mueller at SMX Munich, he announced that one of Google’s next planned steps will be to “send ‘fyi’ messages in Search Console when switching”.
— Simon Griesser (@SimonGriesser) March 20, 2018
Google’s history with announcing updates and changes to their algorithm has often been spotty. Usually, when there is a change made that impacts the rankings of websites, Google’s response is something to the effect of “Google usually releases one or more changes designed to improve our results. Some are focused around specific improvements. Some are broad changes (source)”.
It is interesting that Google has decided to let webmasters know when their site has been moved over to mobile first indexing. This will allow webmasters a good idea of when the change occurs, what the effects are in terms of organic performance, and issues that should be addressed.