I have the same account configured in my ipad and iphone.
In the files.app i can browse, add, and delete files from varios online storage services (included box), but in the recently deleted section appear a folder from box, with one name in my iphone and another name in my ipad.
When I open that folder, it opens my files on my box account, like a shortcut.
I don’t know if it’s a folder.app bug or a box issue.
I can’t delete that folder either. If i look for it in the trash bin through the Box webpage it doesn’t appear, it only does on my Files apps.