@feld @dashie well, Thunderbolt is an Intel trademark that requires Intel's approbation to be issued...
(See for example Framework laptops that were Thunderbolt compatible for months but couldn't market or communicate on it since they weren't approved by Intel)
USB4 cover most of the Thunderbolt 3 spec, and should be sufficient to declare full Thunderbolt 3 compatibility.
That's said, never had my hand on it, but there's quite the tests online that maybe tested this capability.