New to trying to explain this but lemme give it a shot. Quick edit: i'm speaking from what I think but people feel free to correct what I say i'm always up for learning about how this works.
New schools while are limiting in the sense that you are risking what your rotations are since they're not quite established, also give some people an opportunity to apply for schools that may give them some leeway since average gpa and mcat are not established yet, though they are still competitive so it's crucial to not let your guard down. I'll be reapplying myself next cycle and i'll be looking into newer schools after I learned my lesson the hard way this cycle about not having a plan B and not making my list correctly the first time.
Newer schools in my opinion also may not be as bad if the undergrad has a decent foundation already to be making a good medical school as well as good hospitals around the area and the means to be making the connections for their rotations later.
There are however cons to new schools popping up left and right, and if you look into the topic a bit you can see people who articulate much better than me and their arguments on why.
It essentially boils down to what is their plan in the following years, will they do it and whether you want to apply to a new place at the risk of how they may prep for boards and such? Though is there a stigma for new schools and residencies? I was under the impression that if you knock your board exams dead no matter what school then residency opportunities will open?