I assumed Flexon glasses frames are made from some form of Nitinol? They just say "memory titanium" in their marketing, which is pretty much what Nitinol is. My dad had several frames of these, they behaved in that same heating/cooling way you mentioned.
I thought flexon was just very springy metal, not nitinol. Nitinol is not very rigid, it bends easily. And even though it snaps back when heated, it's not perfect -- I've got a few toys made of the stuff and after a while they get damaged and don't return perfectly to the original shape.
Sounds pretty legit to me unless I see something else saying otherwise. I think they just stress the titanium of it as a lot of consumers probably think of titanium as a "space age" futuristic metal that they make space ships and the SR-71 and Lt. Dan's legs out of. Saying its made of Nitinol means nothing to a lot of average consumers.
https://www.flexon.com/