The quote does NOT mean formula is not tested in the lab. It means that there is no scientific follow-up. Yes, there are old anecdotal studies, but for formula to stop being a "trial" you need:

A sample population in a great number
Children exposed to the exact same environments - that includes parenting, number of feeds, solids introduced at the same time, illnesses and vaccinations given at the same time. And, if you want a bigger study, it will include schooling too.
Ideally, twin studies.

I can't really see this happening, so formula is still experimental - there is no true evidence one way or the other. That's the scientific perspective at any rate, which is very different to the mummy perspective!