Aren't femcels fat women that no man would want?

The only time I hear the term, it's coming from Incels culture as a means to trash women.

I also disagree with you. Lots of words have multiple meanings and have drifted away from their historical context. It's not inappropriate to use the most common or current meaning of a word and leave off the historical meanings. For this article, it's a point of interest, inbroufht it up myself in another comment, but not including it does not invalidate or diminish her argument.