Yes, and in other contexts too. The superlative can also mean "the most X possible".
Suppose a law allows a maximum sentence of 10 years. If the culprit is given a sentence of 8 years, he is not prosecuted to the full extent of the law. But 10 years is both "the full extent of the law" in absolute terms, and "the fullest extent of the law" relative to lesser sentences.
Right, of course! I started thinking about it after I submitted my post and thought of expressions such as "the fullest possible extent", which indicates how close to a given maximum level one can get. In such a case, the comparative and superlative could be used.