Yeah, I asked about it a while back myself and I think that was the reason given.
I don't feel the need, though, Our new-posting rate per day is low enough that a periodic check-in seems to work OK and we notify people who follow threads.
In fact, although we're supposed to only send 1 notice, for some time, I've seen indications that every response to a followed
thread notifies me, even if I haven't been back to catch up.