Agreed, and very light on the technical. A few months ago when I was working on setting up a pi-hole with and testing DNS blocking, I came across a few articles like this. Long story short, I could not find a -verifiable-, in depth and even slightly scientific method approved study for the major free services. Ended up going with blocklist on the pi-hole and using quad-9 just for the DNSSEC addition. No problems so far, and not buying into the other snake oil.