Again, the example given cannot make the point intended- its simply comparing apples and oranges.
No Bishop (even if he be the Bishop of Rome) has the right to go against the Catholic magisterial teaching on this or any other matter. What you describe would fall under the category of
abuse, no different than the abuse going on with annulments in Western English-speaking countries that has even caught the eye of the Pope and he has complained to the CC equivalent of the World Supreme Court in marriages that is based in Rome. It certainly cannot be used to support the point intended.
No pope or his brother-Bishops can bend the Divine Law for anyone, or excuse anyone from it- That’s really the argument being made that has been couched in the phrase “permission to sin”. Eve when concessions are given/allowed, they are done so always not to interfere with the Divine Law itself- in other words, the concessions are present in the particular circumstances themselves and the Bishops provide the best guidance of navigating them without sinning against the Divine will (Law)- That’s the work of all Bishops everywhere, and the point of their power and authority vis-a-vis the faithful: To guide the faithful on how best to obey the will/law of God in all types of circumstances, difficult, new and perplexing.
What is meant to be expressed by the objections given here is that the Divine Law remains true regardless of what Bishops purport to do/permit, and if what they permit is contrary to the unchanging Law of God, then in a sense some could see it as permitting sin- because to them, it remains sin per Divine Law regardless of what a Bishop says.

Obviously the true reasoning is not so simple (That is: let us permit sin because it’s easier…etc). But the more basic argument is: What are the Bishops’ powers/authority in the church with regards to the obligations of the Divine Law and the universal natural Law? Obviously for the Catholic Church, the authority of the Bishops remains always perfectly subordinate to the Divine Law and does not ever contradict it.