I hadn’t heard of that. But babies will develop at their own rate so don’t stress

What an interesting question. I think the research on this is constantly changing.

My daughter rolled more than she crawled and she’s quite bright at school, so I don’t know if the correlation between crawling and brain development is necessarily correct.

My sister says a lot of things like this. She is a scientist and has lists of mile stones and ways they should do things. All my kids crawled differently and walked at different times. They are all doing great with their learning and are generally happy kids.