Not surprised as some male reptiles can have more than one hemipene. Crocodiles have been known to have 3.

If they only looked at a few species of snakes, they missed a lot of snake sexual behavior. Many spend hours rubbing their bodies together in orgy like masses. It's not just the males doing the rubbing. Then they'll pair off, entwine, and mate.

It's a wholly male perspective to see this behavior and see "male aggression".

(Mostly) male researchers have a long history of looking at animal mating behavior through a lens of how human males tend toward fetishes, mostly because of all the religious sexual taboos.

The first book on sexuality I read was in the late 70s. It was a pop culture book based on research from the 50s and 60s. I can't remember the title, but it was one of those pulp works. It claimed that chimpanzees were gang bangers, sea slugs were rapists, earthworms were transsexual deviants, and so forth and so on.

We need more open and balanced perspectives doing research like the study you cited.