"Demonstrated" crosswind tells you exactly that and it usually specifices for which kind of pilot (some old POH says usual, some say average, it depends on when it was written). It just gives you an idea how crosswind sensitive the bird is and what is usually safe. But, these are writings in old POH, new ones often tell you "max allowed crosswind" or "standard ops max limit crosswind" and these wordings do have an impact on air incident investigations as well as insurance coverage. In the case of "demonstrated" it is a hint, in case of "max certified" it is a setting for allowed POH operational limits. In first case and an incident you underestimated your skills, a mistake, in second case you violated operational limits. And be asured, a 1955 C172 will be case 1, while an after1986 C172 may be case 2.