CJI : refers to an institution which has been incorporated by Central/ State Act , the substantive part of 23 says you cannot use the expression university, the proviso however contemplated that there may have been universities earlier which were using the expression university though they were not covered ...its a sunset clause, they were given 2 yrs to bring themselves in conformity , in this case AMU is not in the proviso for this reason that AMU had already been constitution by that central legislation, which law continued under art 372, your argument is without this they wouldn't be allowed to confer degrees.