I didn't like this number either, but it's more mainstream than you think. For example, from last year: https://thehill.com/blogs/blog-briefing-room/3868557-most-yo.... This is an opinion article citing a contemporary Pew Research study that appears to support the 60% number, although it's stated as "63% of men under 30 describe themselves as single" (emphasis mine).
I don't think you needed to imply that someone was an incel.
Out of those under 30, I bet there is a huge differebmnce between those between 20-24 and 25-29. It is no secret that women tend to seek people who are slightly older. A few decades earlier, a 20-22y old guys would just date 16-18y old girls and that wouln't be frowned upon nor put them at risk of going to jail.
Naively, you'd think that if demographics break down 50/50 between the sexes, then 60% of men being single means 60% of women are single too. But that's not the case; the article says men in their 20s are single at twice the rate of women in their 20s.
I agree that part of that ~30% difference could be women dating older men. But it could also be women dating each other: this[0] Gallup poll from 2023 found that 27% of Gen Z women identify as lesbian, gay, or bisexual. Gen Z as noted here doesn't perfectly overlap with people in their 20s, but it seems like this could be another (better?) explanation.
I don't think you needed to imply that someone was an incel.