From what I remember, the original study was indeed about cockroach "milk", from a species that births live babies and feeds them a slurry of crystals and proteins. That slurry is the stuff that is technically more "nutritious"

I don't think anyone is actually trying to get humans to consume the stuff. There are a lot of mammals that produce milk that is more nutrient dense than cow milk, it's just not as easy to collect it + theres little reason to do so