In the Harvard referencing style, is it wrong to put references in footnotes?
As your question is directly about Harvard referencing, I believe all Harvard referencing uses in-text citations. Wikipedia supports this understanding.

Yes, you can use footnotes but they are used for clarification or comments, they are not used for referencing as the image in the question has done [therefore the author has cited improperly].

There are several sub-types of Harvard but ALL of them that I am familiar with are in-text, not based on footnotes (except as noted above).