Maybe at first it was a sane reason like this. When we were having a kid, though, we were definitely told by reputable sources (like an obgyn) not to feed the kid peanuts in any form until 3 years old. We decided that the bureaucracy of what advice to give hadn't caught up to the science we'd read, and just tried small amounts of peanut butter when we moved to solids.
An OBGYN isn't a scientist. Move to "solids" is such a weird thing to say. Once you're off breast milk / formula you just go to whatever. The pureed food has to be one of the biggest scams in human history and leads to required orthodontia.
> This advice was never based on science.
I'm like 99% sure this was to avoid babies/young kids choking on peanut