The translation stuff seems to all be handled by your phone, so what is it about these specifically that makes them required for this type of functionality? I'm having trouble seeing why this shouldn't work with any set of earbuds...
That's to say, I don't believe the Pixel Buds are necessary at all for real time translation. But I think they're presented with the real time translation to give people some positive and cool imagery to associate with the earbuds. It's advertising as far as I can tell.
(Other than their choosing it to be so, of course. ;)