.. I would also expect this to be a low-research area, but not due to sounding silly, but rather due to high-noise datasets. People lie about their sexual desires a lot. This particular desire is even more likely to be denied or concealed from researchers than most, so I would expect most people setting out to look into this to get to the "Design data-collection protocol" stage, acquire a monumental headache, and then go research which kind of diet is easiest to stick with instead.

When you're going off of personal observation, how do you distinguish whether preference for number of partners is a (relatively) hard-coded variable in the brain like sexuality, or if it's something highly malleable like e.g. preference to live in a rural or suburban area? Obviously empirically there are people who prefer to be polyamorous, people who prefer to be monogamous, and people who could go either way, but it doesn't necessarily seem obvious to me that there are a whole bunch of people who inherently long to be polyamorous that are being stifled by our monogamous society. (Not sure if that's what you're claiming.)