User blog comment:ThatGuy456/A Guy's Thoughts: (Week 4) "New Amazing World of Gumball in February!"/@comment-28146494-20170305000201/@comment-28485972-20170305005127

Which explains why he was "fawning" over Rob. Because he had history with him. Meaning that he probably felt he had more reasons to be included in his life. So it doesn't really contradict anything established about either Gumball or Rob. They were both just being themselves. Gumball was trying to get involved (this time with his beloved nemesis, whom Gumball seems to view as someone who completes him and Rob was trying to find someone to hate).