That saying doesn't seem to be true at all if you sort by age. If you have your nobel prize by 30 you are an outlier.
There are similar sayings for mathematics that don't hold up. I don't really understand where the perception comes from when it is easily fact checked?
I think the phrasing is a little off; the way I’ve heard it is that most Nobel winners had done the majority of their research before they were 30. It just takes a few decades for their contributions to the field to become apparent.