Can you elaborate on the “x2"? Im curious.

Honestly titanium is not as good as the consensus would like to think. It has its applications but fasteners is rarely the case in structural applications. Most likely this fastener is a PH/duplex/stainless steel.

Not sure if my previous reply went through so here goes...

Except, rolling threads increases their density in the root mostly and up the face to the PD almost. I mean cutting is the one term that implies material removal.

Cavitation. The sudden smack creates a vacuum pocket in the bottom of the bottle and the force of the water rushing back breaks the bottle.