I never assume that anyone in business is telling the whole truth. People say whatever is convenient without leaving themselves liable to be proven to have lied.
Rizzo leaked enough stories, through Ladson, for instance, to make it clear that he wanted to drop Dunn, and to explain that he wanted a better fielder at 1B.
Looking back, that is just what Rizzo did. No real surprise. (Foolish move, yes, of course.)