What exactly are the "potentially derogatory implications"

Well, Connie, I'm an Aussie and I wouldn't personally associate "gone walkabout" with anything derogatory.

That said, a reasonably high profile international Rugby player who left his squad to go home to his family without telling anyone (who also happened to be of Aboriginal origin) was tagged by the media as someone who had "gone walkabout" and I guess the implication in that case was that he was irresponsible.

Methinks it's all in the context...