subsequential normal notification will be surpassed if Critical display on the top banner while screen is on iOS

Hi There Our app is used in the hospital field and receives remote APNS via the Notification Service Extension.

We found a scenario where screen is on, our app is in background, if a "Critical" notification is displayed as a banner at the top of the screen, subsequent normal notifications will be suppressed and no sound will play. Only after the user swipes away the critical notification will the normal notification appear and play a sound.

is this as expected? I could not find any document on such case from Apple.

Thanks.