First it didn't happen while taxing. One A/C was under tow being repositioned to the gate. Apparently the tug driver put the wing of the A/C undertow into the aft fuselage of another A/C that was parked at the remote spot. Neither A/C had crew on board.
I saw it on the SEA news and it happened 3 days before your post SKYFLYR. I would say it must not have been much as there has been no mention of it since. Just my 2 cents..........