certainly there are overlapping aspects but in a poly relationship you supposed to embrace and celebrate certain acts which is entirely upside down compared to a voluntarily exclusive relationship. look up: “comperison”, it’s even debatable among poly circles. again, poly is not a well defined term, there are hundreds of subsets of it, each node and person creates multitude of complexity and agreements (or non-agreements). personally at the very beginning of my little research i had a hard time even to distinguish between being single and being poly, as there are so many overlapping factors on those two too, however now i understand the differences, and i believe being truly poly at the core requires an entirely different mindset, which either comes naturally, or not, but you cannot consciously force it, similarly as you cannot consciously change your gender identity.