I don’t think it’s an “industry term” in astronomy. I suspect it’s pretty much a given when discussing a planet that, unless the planet is referred to as Earth, it’s not Earth. And I suspect in the context of the JWST it’s pretty clear that it’s not Earth (does JWST ever look at Earth?).
JWST can't look at earth without major damage, as it is in a halo orbit around the Earth-Sun L2 point, which means pointing the optics (which are carefully protected from direct sunlight by that fancy five-layer sunshield) at Earth, also involves pointing those optics vaguely at the Sun.
We are for all purposes, the "ET" of others. Excluding creation by a Deity, Machine God or a Simulation, we are also the proof life can emerge in the Universe.
Maybe this is an industry term, but for layman - it sounds like its saying "where ET lives" and we found water on ET's planet.