In a TED TALKS video the speaker says in English, "But that doesn't really make you fluent."
The TED TALKS translation to Russian goes like this:
Но это не значит быть «на ты».
The Google translations are like this:
Но это не действительно сделать вас свободно. (That doesn't really make you fluent.)
Но это не значит, что ты свободно. (That doesn't mean that you're fluent.)
Usually fluent is translated as forms of беглый or свободный. Could it be that на ты is an idiom for fluent?

Another idea is that на ты somehow refers to something said in the previous sentence, but I'm not seeing how this would be the case. At any rate here's the link to the TED TALK video with Russian translation in case anyone is interested in seeing the original context. The sentence occurs at about four minutes into the talk.
LINK: https://www.ted.com/talks/mitch_resn...cript#t-255612
Thanks!!!