I’m not a lawyer so if it matters hire one.
Well yeah Kellogg’s would still own IP ownership of their mascot, it would be covered as to trademark rights, but could not copyright the DCC assets used “IN” MetaHuman used to make the the mascot as the rights are held by MetaHuman. What you could do after the fact is generate and sell clip art in rendered form but not sell the base asset used in the construction as DCC elements. Be like stealing ketchup from MacDonald’s as part of the condiments you give away at your hotdog stand 
So simple answer your assumption is correct but any derivative, like renderings, would be considered new art which you could copyright.