Caltech Core

Hello everyone,
I read that Caltech admits students whom they believe can handle Core. I was wondering whether it would make a difference to my application that a lot of my ECs are physics- and astronomy-related, rather than having a general focus on science and math (which I believe Core comprises).
My grades and test scores are high, and I think they reflect that I can handle Core. I would appreciate if someone could make clear if ECs are important in this context. Thank you!

Successful applicants demonstrate that they can handle the Caltech core curriculum in a variety of ways. Caltech applicants are probably the most self-selected among all college applicants. They’re all likely have perfect or near perfect grades and test scores, so your other activities and accomplishments must be such that they collectively paint a convincing picture of you for the adcom that you can handle the rigors at Caltech. I believe adcom at Caltech is staffed with, and often chaired by, professors. They’re very good at looking deep into the entirety of your submissions, including your ECs, for signs of your academic potentials.