"Please respond to the strongest plausible interpretation of what someone says, not a weaker one that's easier to criticize. Assume good faith."

"Please don't post shallow dismissals, especially of other people's work. A good critical comment teaches us something."

"Don't be snarky."

https://news.ycombinator.com/newsguidelines.html

If my Spanish translator is correct, roughly a little over half of the n=150ish participants developed at a slower rate.

Isn't that roughly what you would expect anyway? 50% of the population is below the median. Take a separate population and measure them against the overall median, and simply through statistical chance, a good number of those samples will have an average slower than the median.

over half developed in a statistically significant way that is lower than the expected "bottom half"

they were out doing whatever their parents were doing and/or people were visiting... they missed almost a whole year of that, and even "post-pandemic" people are sometimes more hesitant about being inside public or crowded spaces like they were previously (especially say, if you have an unvaccinated 5 month old)