In general, the reach/match/safety categories depend on acceptance rates of a college, and the GPA/SAT of teh students.
So a college with 10% acceptance rate will always be a reach for any applicant (except a Nobel Prize winner).
A colleges with acceptances in the 50% range will be a safety for an applicant with stats in the top 50%, a match for students whose stats are around average for the college, and a reach for applicants whose stats are in the bottom 25%.
There is also the issues that colleges with acceptance rates of 10% all have “holistic” admissions, so stats are only part of the equation. Colleges with acceptance rates of under 60% generally accept students based mostly on academics and test scores.
So colleges with low acceptance rates are rejecting students whose stats are in the top 25%, while accepting students whose stats are in the mid 50% range. Colleges with acceptance rates of around 50% are generally accepting almost all students whose stats are in the top 25%. They are more or less automatically admitting the top 12%-13% or so, by stats, of all applicants.
Oof course it’s more complicated. For example, UIUC was very familiar with my kid’s high school, and, based on Naviance, UIUC accepted all students from my kid’s high school whose stats fell in the top 40% or so of their students. So UIUC was a safety for many students from the high school whose stats were within the mid 50%.
Also, if the number of applicants is rising bit admissions are staying the same, the top 25% will be changing, and the range of stats for which a school is a safety (or a match, for that matter) will narrow
So there is a students academics (GPA and rigor), and where it falls, relative to other students who are applying that year, there is the college’s acceptance rate, and there is the rest of the application (ECs, essay, etc).
The reason that people consider colleges with acceptance rates of under 30% or so to be reaches for everybody is that, while it is relatively easy to figure out acceptance chances based on GPA and SATs, alone, when dealing with holistic admissions, the calculations change year to year.