i am not sure that’s how it is done at Pitt, when my brother went. though he started out in Arts and Sciences as a Chem major. i [and my SIL says he DOES give me credit, which i wasn’t sure he did!] was the one who talked him into applying to the school of engineering and he ended up ChemE/PE.
i have never heard it as you have described CMU. actually it is done that way with Pharmacy some places, they have to actually apply after 2 years in, to the school of pharm and may or may not get in. There ARE some schools who accept you directly to the school of pharmacy, but that is not the case everywhere.
personally i think it’s wrong for anyone to expect an 18 yo kid to know what they want to do, from the jump. i think a year or two of taking various eng courses, seeing where your interest/aptitude lies, and THEN deciding, makes much more sense.
For normal 18 year olds, sure. But CMU isn’t for normal people. LOL.