I'd suggest that you are 'in' all of the contexts you've mentioned, and so you then move onto the other three components of working out what action to do next - ie, how much time do you have; how much energy do you have; what is the most important thing to do.

For me, I use a self-developed Excel model for tracking my next actions, and so when in the office, I filter my meta-list to hold just "@desk", "@phone" etc - like you, I could do any of them, so I find it a valid approach to treat each of those contexts in that circumstance as one list.