My understanding is that, roughly, TB3 ⊂ USB4 ⊂ TB4. The USB4 spec is based on TB3, and (mostly?) requires TB3 compatibility, and TB4 is effectively USB4 plus b

My understanding is that, roughly, TB3 ⊂ USB4 ⊂ TB4. The USB4 spec is based on TB3, and (mostly?) requires TB3 compatibility, and TB4 is effectively USB4 plus bells and whistles. I think this goes to the point of USB4 ports with all the optional features qualifying as TB4 ports.