Could it be that Andy suspects that the reason for Becker and Edberg as coaches is not for extra work for the players but for extra publicity. He knows how hard he has worked with Ivan but was "interesting to see who puts the work in" a bit tongue in cheek.
He wouldn't be the only one!
I have seen quite a few people suggest that both Djokovic and Boris know that the association gives them both a lot of extra attention and column inches. I hope it's not the main reason for them getting together, but it's bound to have crossed both of their minds. They must both have seen how both Andy and Ivan got a lot of extra attention, and Ivan very quickly re-inserted himself as one of the big names in the heart of the tour. I'm strongly suspect Boris was more than a little jealous of the respect he was getting.
Ironically, neither Andy nor Ivan would be particularly interested in the added attention, which is one of the reasons it works.