“Many students gave up the chance of HYPSM for PLME, not for Brown.”
And that’s exactly why Brown changed the policy. Brown wants students who want to go to Brown. PLME is secondary. If a student is only applying because of PLME, then they are not a good fit and they are better off at HYPSM.
I’m sure Brown will survive under this new policy, even if it means the acceptance rate for PLME goes up a smidgen because of fewer applicants.