I wouldn't agree either, but I think there's some kind of logic: At a certain point familiarity can be a detriment to learning if it leads to you adding invalid assumptions to your mental model because everything else is so familiar. If everything is unfamiliar however you're less likely to start making assumptions.

As for how true of effective this is, I don't know. Anecdotally however I had less problems learning entirely different keyboard layouts for example as opposed to layouts that are just slightly different.