Internet history pedantry, but by the time the subreddit rolled around, the term and the movement had already been coopted.
Incel started as a term for men who felt depressed about being unable to find a female partner, and the subreddit they created was originally a supportive space for them.
The term was coined somewhere between 1994 and 1997 by "Alana's Involuntary Celibacy Project" as a term for people of all genders who were unable to find partnership despite trying. Alana is a woman, and is effectively universally credited with coining the term and founding the movement. The movement wasn't 'for men', the term wasn't about men specifically, and it didn't start on Reddit. It started off as more of a personal blog, where Alana documented her own experiences and struggles - the site gained followers from other people with similar experiences, eventually growing into a combined forum / support group / community.
Then it got taken over by angry misogynists and the term became associated with them, while the original group just kind of got forgotten about. That original group deserves attention and empathy as well as the term they coined; the latter group isn’t even “involuntarily celibate,” as they play a very big role in their own celibacy.
Those folks have kind of always been there, and have always been a heavily represented demographic - Alana has said in interviews that the men who joined in the early days did have some concerning views and some concerning themes were on frequent repeitition in the discussions the community had. I don't think retconning the movement to exclude those people from the "true definition" is doing either camp any favours. The "involuntary" part of the label isn't trying to engage with whether or not the barrier may stem from factors within their control, but solely confined to the fact that they want something and are not getting it. They are simply "celibate, but not voluntarily celibate".
One quip that Alana made in several interviews while defining her modelling of the community she founded was that she didn't care why someone was an incel, ie "it's OK if you're celibate because you're into horses, but that's illegal" that that person should still be welcomed and included in the community.
I just think more people should give some thought to who that term originally belonged to.
I think that in light of this, it's even more important to be accurate and honest who those people are: Not male-exclusive, not limited to this or that cause of celibacy, not specifically gatekeeping out the misogynists or the beastialists any more than any other group. Just any people who want to get laid but are not getting laid.
That's fine, but remember you're doubting the one person unique qualified to talk about the developmental history of the movement that they launched from the site that they ran.
I don't think that it necessarily was "all" or "most" but simply that the male presence within the movement was sufficiently represented by individuals with those views that it's one of the first thing she mentions in the context of discussing the growth of the movement itself.
Part of her point seems to be pointing out that they invited those views in, very early in the movement, out of a desire to be inclusive - only to be driven out by those views later on down the road.
I bring that up in this context because I don't think that the movement or the term can be divorced fully from the male misogyny that it's associated with today. Those people are not latecomers to the label, they've been there effectively from the start - from the point where it went from the comments section of Alana's Involuntary Celibacy Project blog, to becoming "a community" centered around a shared label.
I've used bold to highlight it in the quote above - that is a big "if" that the person who coined the term says is not true. If it were true, we'd be having a different conversation. But it's not true.
The simple fact is that it's a self-identifier. It's a label that people put on themselves based on their perception of their own life circumstances. The original vision for the term says that neither you nor I get to tell anyone else they're "not a true incel" or to go over their life and tell them the barriers are self-inflicted if they don't see it that way. I guarantee you that the people you want to exclude from the term do very genuinely believe that they are "suffering from external circumstances that put them in the position they're in." No matter how much your or I might see them and think they're clearly suffering from self-inflicted wounds, they are entirely sincere in their belief that their dating life is out of their control and has been a victim of cruel society.
To me? They're the same group. Some members of the group are hateful and shitty. Some members of the group aren't. I'd say that the overwhelming majority of members, from both sides of that divider, are experiencing obstacles to dating or sex that are self-inflicted, even if they also have other barriers that are not. The vast majority of both groups would tell you that their personal circumstances are wholly out of their own control.
The "logic" that group uses around attractiveness and dating marketability and how this or that facet of looks or wealth or social status or whatever is ultimately spurious. If Ricky Berwick get rich, famous, and married - the absolute hard impassible barriers that incels talk about affecting themselves simply do not exist.