I haven't seen any Tern hinge welds up close and personal lately, but I'll certainly be having a closer look in the future the next time I visit a bike store. It's difficult to see looking at images online of the latest Tern folders but I have to say they don't appear to have any extra welding around the frame hinge area. There's nothing visible on the Vektron for example a heavier bike with even more stress to handle.
A new hinge design can be seen however, by new I mean updated from the original version with a greater interlocking surface.
Both OCL and FBL hinges look to have this same idea of a greater interlocking area set further forward.