They are not hugging and their body language says it all.
Tusk is a Kashubian. He always has gone out of his way to point this out so there is nothing brotherly about Tusk when he comes into contact with anyone Polish.
Tusk is a Eurocrat who was appointed by Brussels so he isn't a top Polish politician either.
President Duda is the confident alpha male in the room.
Tusk knows that he himself is the beta male. His face is a mixture of meekness and resentment.
Tusk is in a lower status so has to physically reach out to President Duda. Because he is physically shorter than President Duda, Tusk prefers to stand sideways so he doesn't have to look up to and be gazed down upon by his superior. Tusk also maintains his distance since he is uneasy about his inadequacy and doesn't want to be there.
Tusk only shows genuine respect to someone better than himself when they hate Poland even more than he does.