Whatever makes you think that? "Condition" is a perfectly legitimate expression defining amongst other things, a person's physical state of being. Being in "good shape" is also a common expression originating from the USA, but "condition" is the original UK expression. http://www.oxforddictionaries.com/definition/english/condition
In the Northeast US, I'd use "good shape" to mean he is physically fit (due to exercise/nutrition) and "good condition" to mean that he does not have any illnesses. Of course this is getting very technical - I wouldn't really notice if someone interchanged them, although "good condition" sounds like something my grandmother would say.
I think that for condition, it is "tilstand" that should be used. Which should then asked for the translation of : "Han er virkelig i god tilstand". Which is not exactly the same. Even if I have the same feeling than you and feel that it is more fluent to say condition. :-)