Musk isn't a natalist. The global population is going up. And yet, he complains about not enough births. Because he is a white supremacist. He wants white people to outnumber other races. The current state of affairs would be satisfactory to him if he were merely a natalist.
The population is very hard to count, believe it or not. In many places, the birth rate is well under replacement and in the others it's dropping quickly. Furthermore there's widespread fraud and deliberate miscounting which also makes it hard to really know.
So let's get this straight, you think the global population is not going up?
> In many places, the birth rate is well under replacement
Of course, in some places, this is true. But not globally. We don't need more births to keep population going on. There's a surplus of starving, fecund people globally. Musk amplifies and composes tweets about how white people are going to be a minority (we have been for basically all of human existence, but w/e), and he's even said things like if white people are a minority, we will all be killed. Which only makes sense if the assumptions underlying this claim are that white people are uniquely non-violent (i.e., supreme). Or it's an admission that everyone commits genocide against everyone else. Which is so transparently fictitious that someone as allegedly brilliant as he is couldn't possibly believe it.
The most generous description of him is that he's dumb. The least generous is he's a white supremacist.