I think this is an extremely clever paragraph by the WT writers.
1. Witnesses will continue to have children and the writers know that. The amount of couples foregoing having children is probably not too many. I doubt it is even measurable or they have statistics to back it up. They just know that some couples have chosen to do this.
2. It is the same guilt trip they always use. One example that is very extreme (not having children) and an example that isn't very extreme (increasing activity during the memorial season).
End result: hopefully some witnesses will feel guilty enough to make some sacrifice for the good of the organization (money, time, skills).
That is ultimately what they really want.