He went to "check out", and for a fraction of that time "talk with" the protestors, by the words you are quoting.

To "join the protestors" (implying some sort of direct participation) would of course be something entirely different, and in no way grounded in that text.

It doesn't matter 4 hours v. 4 min

An impartial observer of the situation would most likely strongly disagree with that take. In any case it certainly doesn't sound (from the description we have) that the net duration was anywhere near the former value. More likely it was around 20 min max.