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 have the feeling that they like to throw different things out there because they know it will appeal to different groups. For example they may have an article on how children are a blessing from Jehovah. This appeals to young families and encourages them to raise their kids "in the truth". Then you have a statement like this which may appeal to young couples who don't have kids who want to travel, learn a language etc. Now they have a way to do those things while still being super spiritual. They know that people are going to have kids no matter what, it is human nature, so I doubt they will ever feel the need to encourage having more kids.