Battery Usage App MISSING

Hello.

I had just recently bought a secondhand iPhone 7 model, with the 32gb of storage on 27th April. At the second day of using the iPhone I immediately detect that there's no battery usage app showing under Setting > Battery. It's weird because previously on my iPhone 5s the battery usage app does exist. And to be honest, I check the battery usage app quite frequently because of I'm strict with my battery usage.

I already undergo many attempts, in fixing this issue such as simple restart for the iPhone, hard reset, erase all contents and setting, up until back up then restore my iPhone. Finally, I also had update the phone from iOS 11.2.6 to ios 11.3. Unfortunately, my issue still exist.

Is this software issue or a hardware issue? I'm also not very sure about the battery of my iPhone 7. Either it's already been replaced with non-apple's part or perhaps the battery in use is still the original one from Apple. I could not open up the iPhone to inspect the battery due to the reason, it's still under the third-party shop's warranty where they provide me 3 months basic warranty for secondhand iPhone.

Anyone got an idea? Had already sent the phone to claim warranty but seems like their technician also can't solve the problem.