Without trying to sound like a blowhard, I used to put a lot of thought into my talks and answers, in a way I thought would help people think about their faith. I tried to make talks interesting, and used to get frequent favorable comments about them afterwards. Until I started seriously slacking, I used to put a lot of effort into preparing for FS and RVs in order to try to teach people about what I then believed was Bible truth about the impending Armageddon.
Though I'd been an MS in previous congregations, the congo in which I ended up spending the last 13 years of my JW life never did appoint me as an MS. Reason: I didn't get enough hours. I usually got 8 or 9 a month, until a smartarse young elder told me if that was the best I could do, I might as well not bother. It was advice I eventually accepted.
One elder, who was keen to see me appointed, once told me: "We need to get you a Bible study so we can boost your hours." I'd thought "hours" in that context referred to the lead you were setting in the FS groups, but if I was spending another 10 hours a month in someone's home doing a Bible study, no one would have ever seen me "setting the lead" anyway.
I'd say Flipper's statement is correct. It was all about hours.