I'd be interested to see what weight was moved with each exercise.
The bench is an exercise you can really load up, your back is pinned against the bench the ROM is relatively short, the pecs are heavily stimulated but I don't believe it is a very good exercise.
the fly/pec deck is an exercise that stimulates the pec through a much larger ROM but the load and Tut is much less it makes sense that the load moved has to be a lot less.
the weighted dip is an exercise that is just "the upper body squat" every muscle around the shoulder is working hard including the lats.
the pecs are really working here, but at full extension the lats are also doing their fair share.
i think that is a person is having difficulty doing dips, then it's because it's indicating issues with the shoulder, and not because of the nature of the exercise but due to the weaknesses the bench press causes.