It is not a DDD terminology. Chris mentioned it during one slide, in one talk, to provide some reference for folks familiar with DDD. A context is a module and functions, that’s it. Don’t bring more to it than it is.
As I mentioned on another thread, if people take whatever pattern or restriction and follow it blindly, this change is for nothing, because it will likely end-up on another dead end. If you want to have cross-context relationships, think about pros and cons carefully and move forward. Different teams will balance trade-offs differently.
At the same time you say there is no agreement on best practices, you took a “best practice” comment and disagreed with it. 
That’s the point. Best practices are guidelines. They are very important for new teams and we will provide more of them to those teams as we go but experienced teams should re-evaluate them when necessary.
