Doesn't really help you, but I distinctly remember my congregations COBE saying the bit you mentioned about "wittness" being a verb not a noun. He also added, that that's why we don't inflate our numbers by including everyone who's a baptized JW in our counts - only those who have an active share in the preaching work are considered JWs. He said there's 8 million JWs today, but there could well be 20 million people out there who have studied with us and even been baptized, but if they don't preach regularly then they're not considered JWs.
Like I said, doesn't help you a ton, but this guy isn't the type (and I doubt he has the faculties) to come up with stuff on his own, I'm sure there's been something printed about this at some point. He's an old guy, though, so it might've been 50 years back.