The first definition in the very first sentence of the article you linked contradicts you. It defines normal behavior as "consistent with the most common behaviour for that person" (emphasis mine). That is, the first definition definitely doesn't depend on other people, but simply what is common for the individual.

In that way, "normality" is flexible: if you change your behavior in a consistent way, your new behavior is normal by that definition. You didn't become "abnormal" you simply redefined your normal.

Now the article goes on to mention that you could also define this relative to a larger population, etc, which supports your point - but the very fact the headline definitely doesn't align with your claim shows that this is not as straightforward as you make it out to be.