Lanefan
Victoria Rules
Well, given the definitions 5e uses, this is about right. Whether it's the best definition, or even a useful one, is an open question.Part of the problem rests in how exploration, as we are reminded by others in this thread, amounts to "everything else" that is neither Combat nor Social.
First off, there really needs to be a fourth defined pillar - Downtime - to cover all the non-adventuring activites characters get up to. As it stands now, if everything has to fall under a pillar downtime activities mostly come under exploration and that doesn't make sense.
From there, it becomes simpler: the Combat and Social pillars are largely built around the concept of encounters, making it pretty easy to know when play has engaged one of those pillars. Exploration, however more fuzzily covers most of what happens between encounters. And this might be in part why some see exploration as unimportant or redundant if one is starting with a "get to the action (i.e. encounter) now!" mindset encouraged by 4e and other games; as jumping from encounter to encounter skips over, by default, a lot of - or all of - that which happens between.