All the other examples (in the sample article) have the interactive
pieces in a exercise, not in an Activity. Those need the enclosing box,
but there may be differences of opinion abut the blue background.
So, I think we need to see more examples of how these are used.
In particular, are alone and inside an Activity, the only options.
There already are special cases (which required changing the HTML)
for Parsons problems, and Active code, because those naturally
have a different width.
Where I am heading is that this is not a simple or isolated decision.
Another complication is that the oscarlevin style does not
treat these differently, but it should.