At least a subset do. The study concedes it's self-reported and not necessarily a representative sample of all incels.
At the very least, it sounds more to me like there's now just cross-pollination between the old PUA community/philosophy and the incel community. Both are highly misogynistic, but incel culture is literally defined by men unable to find partners and PuAs are defined by men who only find many multiple partners.
A mysoginist claiming to have multiple partners just sounds like a Red Piller to me, not an incel, and I'm a bit suspicious of this whole "study". I'm curious whether this study even bothered to consider that distinction. I read the article top to bottom and found no indication on how they actually identified their sample of incels as incels, and couldn't find a link to the study itself. It appears like they simply found some online mysoginists and assumed they were all incels.
Contrary to the incel narrative, the study found that extreme misogynistic views were driven by a psychology of dominance and status-seeking, which correlated with having many sexual partners. The study suggests that individuals who hold these extreme views are more similar to socially dominant "Chads" than to the stereotypical incel who turns his sexual frustration into hatred and a desire for revenge against women.