As others note, the definition of Jupiter’s radius is set by where the pressure is 1 bar. This is somewhat arbitrary, but the arbitrariness doesn’t matter much: the pressure drops to 1 microbar just 320 km higher, which is <0.5% of Jupiter’s ~70,000 km radius.
Yes, that's why I said buff. The radius as defined would increase, because surface pressure is 90 bar, so at 1 bar, you're pretty high in the atmosphere. I can see merit in such a definition because that is the level at which we wouldn't have to pressurize our space stations to be comfortable. (Really 1/3 bar is fine too.)
