I would be extremely surprised if HMC had any bar-lowered classes.
Just because you offer both a linear algebra course and a course on groups and rings doesn't mean the linear algebra class is some kind of mickey mouse credit--it's just for people who haven't seen that material before.
[0] https://www.hmc.edu/institutional-research/wp-content/upload...
MAT215-217: Recommended for math majors, some prior experience in constructing formal proofs is useful but not required.
MAT216-218: Accelerated math major sequence, for students with substantial background in university-level proof-based analysis courses.
MAT214-204-203: Alternative path to majoring in math, with a more algebraic introduction to proofs
MAT203-204-215: Alternative path to majoring in math; good path for the applied math certificate.
https://www.math.princeton.edu/undergraduate/placement/seque...
Lumping all these students into one general course would be a disservice to everyone, like you say, and should be spilt up.
Preserve the ability for those with this level of prior experience or aptitude to thrive, while providing support for those who do not have this head start but could either (a) Catch up, given the right initial environment and ramp up, or (b) never catch up to the most well equipped students, but will still be proper graduates of the program.
The people with prior experience can take classes that are suited for their level, and will be challenged rather than bored and resentful of their classmates.
The people without prior experience can ALSO take classes that are suited for their level, and will be challenged rather than intimidated and condescended to by their classmates.Once they have some experience, they can move on to the other classes.
It's a win win for everyone, including the people who through whatever luck or drive have experience before they enter the system. Remember, not everyone has the same access to things like books, computers, and programming classes in earlier environments like high school. Making an actually introductory path helps level the playing field without lowering the bar.