This specific article was based off a study conducted in Austria with mean ages of men/women involved in their 20s. IDK what this says about world cultures as a whole, or even the culture of Austria as a whole. I would assume that the possibility of people late stages of life might have different feelings on the matter exists and they don't mention it as a variable they accounted for. Never mind all the other variables that one could suggest might affect this matter that aren't specifically mentioned in the abstract. And, in fact, they mention that this paper they're presenting is the first to really delve into the subject of ex-partner feelings, so their results might be completely disproved as more people look into the matter.
Personally, I think grouping all men together isn't constructive a lot of the time.
Sexuality and gender attributes aren't binary. Most attributes can be defined on a scale. I think this was the nub of the OP's argument.
And it's worth noting that the study only focus on heterosexual people, so a more accurate title would be "Heterosexual men hold more positive attitudes towards ex-partners than heterosexual women do"
At some point you're just going to have to read the paper if you want full accuracy.