Well of course. As a phrase, it's meaning isn't clear just from the words in the same way that "give me that pen", "make your bed soon after waking up", or "brush your teeth twice a day" are. All of those scentences are made of phrases and words that have meanings and the meaning of the scentence follows from composing the meanings of its parts.
"Be yourself" as a piece of advice has a literal meaning equivalent to "breathe and metabolize"-- a person is by definition themselves. So the phrase must mean something other than it's literal meaning, but what?
As an adolescent, the only explanation I ever got was "don't try to be something you're not". The problem here, is that it contradicts so much other advice in your life. As an example, 16-year-old me was a shitty driver. Should I have stopped trying to be so shitty at driving? Of course! The phrase argues against growth in general and I'd seen people use it as an excuse to avoid growth. So 16-year-old me concluded that the advice was meaningless and that the people saying it weren't saying much of anything besides "chill out, relax".
But considering who poorly explained it is and how often it is given as grand life advice, it isn't at all surprising to hear someone else take a drastically different meaning from it.