And it allows it to lift the backcover with the headphone jack.

Oneplus shows this technique in their videos, e.g. the one showing how to swap the original cover to use their bamboo cover.

Yes. The photo shows the speaker upside-down. But its not possible to mount it that way.

I think it is IMPORTANT to mention the following:

The speaker is stuck with some adhesive.

By trying to lift it up it is very easy to destroy this fragile component.

The problem is, the metal frame of the speaker is stuck by an adhesive sticker. And by lifting the black plastic, the two parts break up! If your are unlucky the super thin copper wire breaks and the speaker is dead.

So please. Lift the speaker underneath the metal frame which is hardly visible.

And also take care not to perforate the membrane.

So it is necessary to be very gently or to buy a new speaker