Getting surgery immediately after changing insurance?

So my current insurance sucks, and I’m getting on my mom’s insurance for 2027 to get hysto and phallo. My original plan was to get hysto in March over my spring break at college, but I just realized my winter break extends pretty far into the new year, and I might be able to get it done then. For anyone who did this (surgery in early January immediately after new insurance coverage), did this work? Did insurance cover it despite being so early? I’m not sure how the preauthorization will go.