@HPuck35, thanks for your perspective.
In my son’s case there is no doubt that it was largely his deep commitment to (and excellence in) his STEM passions that made him attractive to MIT (and Caltech). Yes, he also plays piano for pleasure, but it didn’t make it into his application, and didn’t come up in his interview.
Far be it from me to read too much into the admissions tea leaves (see above about “applying sideways”), and I am sure there are anecdotes to the contrary, but it is decidedly unnecessary (and potentially counter-productive) to try to project a “well-rounded” persona if that is not your thing.