I wonder if the VFX department didn’t get the memo.
It could also be an early script draft and during production they decided not to spend time and money on changing the ship model. Not everything you see in a script will end up on the screen.
It was present at the end of the episode where Voyager got the future Borg technology. This scene from the linked script is the scene from the very beginning of the episode which depicts a timeline in which Voyager returns to Earth without that Borg encounter.