Does the severe expiation become obligatory for one who had oral sex with a non-mahram woman during the daytime in Ramadan, resulting in ejaculation?

Whoever ejaculates by kissing or direct contact without intercourse during the daytime in Ramadan must repent to Allah and make up for that day. As for the severe expiation (kaffarah mughalladhah), scholars have differed concerning it, and the preponderant opinion (al-mufta bihi) is that it is not obligatory, but he must increase in repentance.