I was wondering something similar - could it have been that in the first half of 2020 people put off having a kid and then after lockdowns were lifted, made up for lost time?

For a little more cynicism, that fits with their finding that the "boom" was most pronounced for first-time parents, aka the ones that weren't stuck home with their kids...

Not sure why so many people balk at the comparison of having a dog versus having a kid. You don't need some deep philosophical reason for either: humans have lived alongside dogs for thousands of years, and humans don't need a justification to reproduce any more than a dog would. We're animals, we make babies.

I did not opine on whether or not people should have had a baby or for what reasons.