The children in question are from what he's said exceedingly small so far; possibly being thrown up on repeatedly and not having any idea which particular pattern of rocking is going to make your child stop crying this time is something he finds far more frustrating than you do - geeks often do feel that way because they want to be able to apply rational approaches to fixing things, whereas with such a small child that doesn't exactly work.
I really like children from about the age of 2.5-3 up, but before that they're ... impossible, not in a sense of "impossible to deal with" but in a sense of "this is so completely unmodelable logically that I am unable to it it into my headspace". I have absolutely no idea how I'm going to deal with this if I eventually decide to attempt to procreate.
Yet kids that young are logical. They want food and love, and they want to know that they will get those things. If they have those and still cry, they're sick. Later, it gets more complicated.
Plus, when they're your kids, they have half your genes (usually), and it's easier to grok them. I had that "no idea how to deal with a kid" geek/engineer perspective, and it went OK (kid was colicky, so it wasn't easy, but it wasn't irrational). But also note that in the grokking is the empathy (no need to fix anything other than the food and love and providing them consistently)--raising and loving a child is not rational.
If you really like kids that young and you're not a parent, then you probably don't have much to worry about. I never understood the nonchalance of parents who had just been puked on. But when I found myself there I understood.
I really like children from about the age of 2.5-3 up, but before that they're ... impossible, not in a sense of "impossible to deal with" but in a sense of "this is so completely unmodelable logically that I am unable to it it into my headspace". I have absolutely no idea how I'm going to deal with this if I eventually decide to attempt to procreate.