Hi there. The changelog you linked to isn’t something we’re really using. Changes we make to the Unified API are not necessarily reflected in that changelog.
Currently, the best way to find out about API changes is to keep an eye on this forum. For example, in the past few months, we’ve posted here about a couple of improvements to the Journey Planner functionality:
That said, we are trying to find ways to better communicate changes. If you have any thoughts, please let us know. 
(cc @SarahLS)