Looks like they are talking about this sort of thing:
The Seven Clusters of Dogs [Archive] - Pets-n-People
It says:
"Cluster 1: (high reactivity, low trainability, medium aggression) Lhasa Apso, Pomeranian, Maltese, cocker spaniel, Boston terrier, Weimaraner, pug, Irish setter."
Although I personally would not class the cocker spaniel, Weimaraner, or Irish Setter as 'low trainability' especially the working ones, although I suppose you could argue that they are not particularly 'trained' as such, their work is more instinct/inherited behaviour rather than 'training'.
There are some breeds such as Chihuahua's that I would include in that description though.
I suppose you could tell how they would manifest in the dog by looking at the breeds mentioned and describing their behaviour.
To be honest I don't like to put labels like this on dogs/breeds - what one person would class as 'low trainability' is different to what another person would think - and what on earth is 'medium aggression'?
My other breed Anatolians are often said to be hard to train, yet a lady in Germany has trained hers to the level of free running beside her bicycle through a town!
Also many dogs classed as 'low trainability' are just extremely intelligent and independent.
Sorry, not much help I'm afraid!!!
Sue