I’ve owned and wore Lindberg Air (ha, Apple wasn’t the first to come up with that name!) titanium glass frames for years, and even though they’re basically made from ø1,5mm/0,06’’ wires bent and twisted together industrially, they’re ridiculously springy and resistant to accidental bending (not to intentional bending though, as opticians are still supposed to be able to, you know, adjust them to your face, but did I mention they’re basically thin, circular cross-section wires?), so… this doesn’t surprise me in the least.
Titanium is one hell of a material, with very interesting properties, and it makes me a bit sad that it’s gone from the iPhone Pro line, but I suspect it will live on in this premium (a different kind of premium, but still premium nonetheless) line and maybe on a future foldable iPhone, some future iPad, etc.