It's statements like this that make me suspect they really believe their own nonsense. If they were cynical about the end times and more interested in growth, there's no way they would discourage having children, is there?
I wouldn't go that far - discouraging children makes good sense regardless of whether the GB really buys their own BS. They're older and if they're just in it to keep themselves cared for, they would only be worried about the cult's sustainability through the end of their lives. So, 20-30 years is all they really need. If they were to encourage parents to have kids, most of those 20-30 years the parents are going to be investing in their children and not in the cult, and the children that stay in the cult (a small percentage of those born-in) would barely have a chance to yield any return on that investment before all of the current GB is dead.
Furthermore, it appears that most of the things they've been doing lately are narrowly focused on maintaining short-term viability at the potential expense of long-term sustainability. This would just be another such move. For me, it's extremely difficult to tell if the GB are really true believers or not.