Except...the bit talking about children specifically mentioned them making their parents (and probably other colonists) quite happy. So having some healthy children around could be functionally useful as a constant morale boost even if the child isn't going to be meaningfully contributing in any other fashion.
I'd still expect that the game will do something to give them some sped-up path to reaching adulthood, other than just the vats, but I wouldn't be surprised if it was something you could configure. Some people do just enjoy a realistic challenge.
Well first, if you're in a situation where morale is a serious concern you are not in a situation where "raise a kid" is a viable option especially not when the logical negative outcome is "colony is not super jazzed the kid died."
Second, "I need slightly more food than I thought I did" is not an interesting challenge. The post talks about raising and teaching kids, without vat growth that's just not going to be a thing anybody does because the time scale just isn't something you're likely to encounter. If only 6 year old forts ever need to worry about educating kids almost nobody will ever deal with that unless they're accelerating them specifically to do it. If some folk getting pregnant means that within a few quadrums you need to be ready to set up a schoolhouse- that's a challenge it's something to engage with.
Either we have horse years or natural kids are mostly irrelevant.