Rita's eyes instantly lit up when he heard the description of Infinite Pleasure. Although this ability wasn't as helpful as Charm Perfume, but in a sense, it was even more precious than Charm Perfume.
Because she didn't need to fall into a meditative state and remain static while cultivating as long as she had yang essence, and she lacks anything but that.
Cyrus was also quite astonished when he confirmed it was Infinite Pleasure because this ability was one of the core abilities of Devil's Spouse Technique and very hard to awake, but Rita did in the foundation-building realm.
As a creator of the DST, he knew better than anyone that the innate abilities of DST were random, and they manifested according to the practitioner's desire and talent. It doesn't matter if they had the complete technique or not.
This loophole was also left behind by Cyrus for a special reason, which will be revealed in time.
