Depends on how things are run. My wife works at the hospital and works 12 hour shifts, rotating days and nights. You’re expected to show up 15 mins early so the previous shift can hand off their patients to you.
I’m not sure how you’d do 12 hour shifts with overlap unless the overlap was considerable or shift times were all over the place. The hospital here gets a certain budget and it makes sense to have it running as optimal and efficient as possible. You also get paid from punch in to punch out so coming in early gets you paid more. Realistically her shifts are 12 hours 15 mins.