Gap years are not necessary. The majority of students that my S graduated with from med school came straight from college, just like mom2collegekids’ S. What is necessary, however, is a competitive app, period (and I’m not just talking about GPAs/MCAT). A competitive app is something that may require gap year(s) because of need (eg grade repair), or sometimes simply by choice. So how necessary a gap year is, is student dependent. There is no one size fits all kinda answer.
Maybe this link will be helpful
https://www.aamc.org/students/aspiring/324772/gapyear.html