iPad lock screen, Bar under battery symbol

I guess you wouldn’t already “know” since you’re asking this question...

The unnamed bar only appears on the Lock Screen when this access to the Control Centre (when locked) has been enabled in Settings:

Settings > TouchID/FaceID & Passcode - scroll to section entitled “Allow Access When Locked” - switch Control Centre to ON

Switching this setting to OFF disables access to the Control Centre from the Lock Screen - and removes the indicator bar from the Lock Screen. The bar shows that you can access the feature (if enabled) from this screen.

The bar, to which you refer, serves as a reminder that you can touch and “pull-down” to reveal the Control Centre:

That indicates how to get to the control center. Swipe down from that spot to get to the Control Center. That bar just shows how to enable it. You can swipe down from any screen to get to it.