If a company explicitly disallows the use of AI in promotional material (which would include backgrounds) and makes a good faith effort to police it then there's no issue.
The problem isn't that sometimes AI will slip through, the problem is you're not even trying to prevent it from being used in the first place. It won't have to "slip through" when you've very clearly stated that it will just be allowed anyway. I'd be perfectly okay if you said "We're forbidding the use of AI at any stage, though we ask you to understand that catching the use of AI isn't always an easy task and give us your understanding if something does get by us."
But "Eh, backgrounds aren't as bad so whatever." is not an encouraging position to take. It makes it pretty clear that you're trying to mitigate backlash rather than actually taking a principled stance.
Again no one is ENCOURAGING the use of AI in those shots
In the same way that you weren't E...