It's also going to make those you convince of this less genetically fit than those who ignore the advice. So the people who choose to have ten kids are going to be more represented in the population a hundred years from now.
Arguments like this are insane because complex behavior like lifestyle choice is not 100% (or probably even 50%) genetic. It’s like saying that the only way to have more people coding is for coders to have kids. Complete bullshit.
In principle there is a selection pressure against it if it's even 1% genetic. But that pressure might not be strong enough to have a large effect very soon (especially when very few people today seem to be actively motivated to have as many children as would be physically possible for them).