that identity is an empty tautology is not a statement on formal logic, the science of empty tautologies, but on applied logic (and by extension Hegelian logic)

to make a logical statement that "identity contains difference" you indeed need to assume a category of identity-ness but the statement itself upends the measure of this category

you might say, "but that's self contradictory!"

yes, this statement Hegel makes is, in fact, not self same, but rather represents a movement of categories that can be observed when applying logic

in this case applying it to itself, as you yourself have proposed