Not sure about the US but in France there’s absolutely no way this would be confused with Apple Thunderbolt. No one talks about it, and I don’t even know it it’s even a thing anymore since USB-C.

As for Thunderbird, it’s not the same name? Idk what to say

My first thought was "why would Mozilla support a proposal to expose Thunderbolt to the Web after rejecting similar proposals for USB and Bluetooth?"

So yeah, especially in light of the lightning bolt logo and "thunderbolt.io" domain name, I think it's confusing enough that I'm honestly surprised there's no "Thunderbolt is a registered trademark of Intel Corporation used under license" notice on the site.