Family Tree DNA Reports Ancient European Origins

Announced at the FTDNA International Conference on Genetic Genealogy this weekend, and now available to everyone who has taken the company Family Finder test, is what is identified as an ancientOrigins report. It's described:

The European Continent has been witness to many episodes of human migration, some of which have spanned over thousands of years. The most up-to-date research into these ancient migrations on the European Continent suggests that there were three major groups of people that have had a lasting effect on present day peoples of European descent: Hunter-Gatherers, Early Farmers, and Metal Age Invaders. 

If I read the online material correctly Hunter-Gatherer corresponds to the Paleolithic, or Old Stone Age, after the last Ice Age and up to 8,000 years before the present. Farmer corresponds to the Neolithic or New Stone Age, up to about 5,000 years before the present. Metal Age Invaders refers to the Bronze Age, up to 3,000 years before the present.
For each of these there's a map showing a trajectory by which those people entered Europe as well as locations where ancient remains have been found.
In my case I'm 16% Metal Age Invader, 45% Farmer and 39% Hunter-Gatherer. That leaves 0% non-European.
The basis of these estimates isn't clear despite a few fairly cryptic tweets from the conference. Is it solely autosomal analysis of the ancient remains? Is it that plus something else, or something else entirely? There's no indication of the likely range of uncertainty.
These are interesting estimates, and may well actually be accurate, but without documentation of the basis on which they rest they are a curiosity.