Francis, great video and I agree with Peter, neither looks right to me.

In the video, you say you’re not pinching–while that is true, it appears to me that both of the movements you demonstrated involve miving your lips closer together top-to-bottom, rather than tightening the aperture horizontally towards the air column.

Inevitably, you would wind up cutting off vibration as you ascended while playing if you used that approach, I believe.

When you engage the corners as you ascend, you will feel your lips push forward to the mouthpiece (or your fingers, as Peter outlines / Greg demonstrated).

Less is more / the 1% rule is important to remember, but when first getting the sensation dont be afraid of overdoing it–which will be a pucker / fish face, but even then you’ll probably experience some easier/faster harmonic slurs which will clue you in that you are honing in on playing optimally.

Hope that helps! Good luck!