Considering this is the third time they’ve been caught stealing art, I don’t believe it was the work of a former employee.
It’s been four times actually.
Bungie has been accused of lifting artwork four times now. Last year, an artist accused the studio of borrowing its designs for a Destiny 2 Nerf gun, which was amicably resolved.
In 2023, an artist pointed out the similarities between their artwork and a piece that appeared in a Destiny 2 cutscene. Bungie resolved this by compensating and crediting the artist.
In 2021, fan art was used in a trailer, which Bungie again resolved after reaching out to the artist in question.
So these are only the times they get caught.
Likely placeholder art making it into production because no one is checking, rather than a deliberate policy. But still bad form.