The important thing here is to know how did they measure young people's political ideologies. I wouldn't expect it was self-perceived as currently, people have a hard time admitting they are conservative compared to admitting they sympathize with a conservative party.
If it was determined by a questionnaire, it would be interesting to see what questions were included. Maybe the questions weren't well planned and that's it. Maybe they equalled feminist takes to progressive liberal ones, which is something that can be discussed. In this case, I would be picky about the origin of the graphics.
If the importance of women's issues like reproductive freedom were overrepresented relative to other issues, this would definitely account for at least part of this difference. But "importance" itself is already a very subjective concept. It's hard to put numbers on these things and create a scoring system that's actually useful.