The movie sucks, but this title is just piling on, cuz this lack of credit isn’t super unusual.

From the article:

The Claptrap model Reid worked on appears to be the one used in the final movie, and Reid speculates the omission may just be because he and the artist left their former studio in 2021 and “it took the film this long to come out”. In response to someone trying to pin the blame on Randy Pitchford (!), Reed stresses this is “a common problem in the industry. Definitely not the fault of any singular person, and would be wrong to suggest this.”