One should realize that one does not pasken halacha (for example whether it is ok to lie) based on a story about a gadol’s behavior (for example, Rebbe lied to his mother that his brother was alive). every individual situation would require asking a shaila from a rav.
speaking of lying about one’s age for shidduchim, a friend was once told that since “everyone” assumes that people lie about their age, they will automatically add a few years to whatever age they are told, assuming that will be more accurate. So if you really are 29, and say 29, they will assume you are really 32. So it would not be lying to say you are 27, since then they will get the age right! A bit of a joke, of course.