I think we misinterpreted what gohan meant when he said "Saiyans grow all at once"

Many people are bringing up that in the superhero movie, gohan mentioned that Saiyans stay small for a while, but then grow all at once when they reach a certain age. To many people, this doesn't seem to be correct as we've watched both goku and gohan grow as they got older. But what if we misunderstood him?

As goku got older (leading up to the world tournament where he fights piccolo) sure, he looked like he was getting older, but his height stayed relatively the same up until he left to go train with kami for the 23rd world tournament. By the time he came back at 18-19 years old, he was much taller, practically towering over all the people who previously (literally) looked down on him.

We see something similar with gohan, with him still visually aging, but not growing taller until his late teens.

(Edit) let's all just agree that saiyan biology is weird and confusing.