That does sound like a fun bug.. as long as he was still beatable.Destiny 2 had something similar, I guess.
A while ago, they released an update that accidentally increased the size of one of the bosses. Players on the subreddit cried out for it to be permanent, but unfortunately, Swoletheon was eventually patched. (for reference, the glowy light effect as he spawns is how big he's supposed to be)