Are there cases in which it is preferable to perform a Sunnah over an obligatory act, contrary to the rule "what is indispensable for the fulfillment of an obligation is itself obligatory"?

Generally, the fara'id (obligatory acts) and wajibat (duties) are superior to the sunan (supererogatory acts), due to the words of Allah Almighty in the Hadith Qudsi: "My servant does not draw near to Me with anything more beloved to Me than what I have made obligatory upon him, and My servant continues to draw near to Me with supererogatory deeds until I love him."

Some scholars have mentioned a few rare cases where a supererogatory act is superior to an obligatory act, which are: a. Performing ablution (wudu) before its prescribed time for one who is not excused; in this case, the recommended act is superior to the obligatory. b. Releasing a debtor in straitened circumstances from their debt; in this case, the sunnah is superior to the obligatory. c. Initiating the greeting of peace (salam); in this case, the sunnah is superior to the obligatory.