Ok I figured it out... holy crap GROQ is amazing. I still love GQL for what it is, but I think GROQ is the best thing since bread, sliced or otherwise.

export const getCats = `// groq
    *[_type == "category"]{
        _id, name, slug,
        "products": *[_type == "product" && references(^._id)]{
             _id, name, slug
        } | order(_createdAt desc)[0..4]
    }
`