Omniscient lovers cause equal problems. The best romances, though they may involve rescues, provide lovers who improve. Darcy learns to communicate outside of his man-cave. Elizabeth learns that she may--despite her quickness of thought--misjudge situations. They come to an understanding.
The omniscient lover overrides all that. This lover may sometimes express doubt, may occasionally--after knowing exactly what the significant other wants, borderline stalking the significant other, arranging the significant other's life--say, "But if you don't want to--"
But such token "I guess you have free will" statements don't suggest a personality in need of transformation or adaptation. Such lovers are rather dull.
However, I do understand the creation of the omniscient lover better than the creation of the omniscient detective--why it is such an attractive proposition. I believe that at the back of original sin or the natural man--the stuff that leads people to behave stupidly and meanly--is a desire for ease, for guarantees, for absolute and all-encompassing answers.
Life is just so hard! And people often wish it could be simpler. Label the bad guys. Force the perfect utopia on people. Go with the latest peer pressure/trend.
Dorothy Sayers called this behavior "snatch." And it's understandable--even if wrong (and explains the number of people who have convinced themselves that Chat GPT "borrowing" other people's work for their benefit isn't lazy, short-sighted, and unethical: what will humans do when the work becomes one mass of circular reasoning?)In romance, searching and dating and breaking up and searching and dating and trying to make a relationship work is hard. It's exhausting. It's understandable that people sometimes fall back on a trope where the desired partner simply makes it happen.
Of course, few people truly want that "simple" solution when it does appear.

