crawling

I try very hard to discount anonomous research from which reporters draw conclusions intended to make me feel bad about myself. But this one just will not let go of me:

Do babies really need to exercise? The facts and questions about Wee Exercise video's: "Research shows that crawling is not only linked to reading skills but that children who miss the crawling stage may exhibit learning difficulties later on."

I try to be relaxed about it, but it is driving me crazy that David won't "crawl" properly.