I disagree. Di Resta has driven at the top level in DTM for a few years already, OK he's a rookie to an F1 car but he is not a rookie to this level. Koba is the other way around, a full season in F1 but little experience to speak of prior to that.
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Your argument suggests that there is no such thing as a 'rookie' in F1, since no-one ever enters F1 without having competed elsewhere!
This year Kobayashi is not a rookie in F1, since it is not his first season.
This year di Resta is a rookie in F1 because it is still his first season.
P.S. German Touring Cars are nowhere close to F1. Any form of open wheel racing is closer: even Formula Ford and karts!