If it’s okay to have vague mystical concepts with no explanation, then what’s wrong with leaving it as-is and the “dyad” referring to something more than the mind-bridging? Not everything needs a “Snoke did it” explanation, but “Snoke did it” is the explanation for the mind bridging, so the dyad must be something deeper than just mind-linking if you’re assuming Palpatine knew everything Snoke knew. Heck, Luke projected himself too, so why wouldn’t Luke be a “dyad” with everyone on Crait? He also saw Kylo in the hut, so were Luke, Kylo, and Rey a three-way dyad?
The dyad concept is not being improved by making TLJ’s story worse, because TROS still never tells us exactly what a dyad is. Undermining TLJ based on assumptions about what a dyad might be, assumptions which are logically incorrect anyway given what has been established in canon, just doesn’t sound worth the damage it does.