I would have thought so too. It is possible that we are more common than we seem, but that we tend to test as fours because most Enneagram tests seem to associate One-ness with SJ-like questions that alienate us.
It took me a long time to realize I was a One. The tests kept misidentifying me based on my negative answers to some of the "do you act like a crazy, neat-freakish, list-making, 'take your fucking shoes off so they won't stain my spotless white carpet that I vacuumed twelve times today!' unhealthy SJ-type?" questions.
XD Oh, those famous organization questions which makes anyone without mild OCD unlikely to relate to...**sighs** I personally never saw what needing to be good and fair has to do with a cleaning obsession...but according to some, it's amoral to have more spontaneous "schedules" for mundane matters...**rolls eyes** INFPs, Ones or not, are likely to have a better sense of priority than that. I find passing my time pondering on values & moral matters and advocating causes more significant than focusing on the alphalbetical order of my courses labels on my binder...Or immersing myself in my passions/improving skills for career goals more pressing matter than doing dishes(apparently doing dishes hands-on is a tad cleaner than actually using the dishwasher so it's worth taking the time to do it...**facepalm**) Well, I really should stop ranting before my knuckles twitch with sheer exasperation.
Although 1 is not my core, I too didn't identify with it right away-as a fix. I always test as(and first thought I was) a 4-5-9. I beleive my 9 result to be higher than the 1 precisely because of the 1 stereotypes you mentioned. Something felt off when comparing myself to other alledged INFPs 9fixed(or just other INFPs in general), though. I think I give a more...self-righteous, serious and know-it-all-ish vibe. I also think I'm more excessively justice & objectivity-oriented than most INFPs(i.e., focusing on justice before empathy or mercy, although I greatly care about all three things). I think this is my 1w9 influence.
I also had trouble identifying with 3 as a core because of the shallow, appearance-oriented,materialistic 3 stereotypes. 3s are reputed to be amoral and non-authentic, things that clash with my values. And somehow no one seems to think of the possibility of threes integrating a moral dimension in their needs to be the best/ideal. I want to be the best in my field, and best everyone in certain traits I value, sure, that's vain. But I also care about becoming a strong moral model. Contrary to what some enneagram authors would like everyone to beleive, Moral 3s exist!
You've mentioned in your previous post that you had trouble fitting in even surrounded by INFPs. This makes me curious. How do you think your core 1 makes you differ from most INFPs? (If it's not too personal)
edit: Maybe I do. I've already edited this post about nine times in an attempt to make sure it doesn't accidentally offend anyone.