LOL I thought you meant a 4 and half YEAR old when I read the title?

I think the reason they recommend the 6 mth mark is because they have gluten and wheat which some children are allergic to, so the things with higher risks they recomend later?
Another reason is some babies under 6 mths can have the tongue thrust reflex still?
another possibility is that teething is most common starting at 6 mths, Felix had first tooth at 5 mths, and had first rusk then too didn't start solids till 6mths though.

These are only my suggestions, and it's up to you and Liam's abilities, some babies are ready for things far earlier than others!