switchup I didn't say it was better for battery life, what I said was that for background push to work via websockets, which is the methodology used when FCM (Play Services Push) isn't present. Without it you won't get prompt notifications but you'll get them all only when the app is launched and placed back in the foreground state.
I personally don't see the point of hobbling functionality for battery life. I run Element and Signal with battery exceptions and still get a full day and approx 5 hour SoT (Screen On Time) while doing other things too on a 4a. I can on less intense days get a couple days and more. Don't read into the percentage either as it is relative.
May take some experimentation, and your mileage may vary as we all have different needs, requirements and usage habits.