The reported altitude of 7,5 km wasn't made up by the newspaper "De Telegraaf". It originated from the official Dutch news agency ANP. The Telegraaf report is almost an identical copy of the ANP news release and was also carried by other Dutch newspapers, such as "Algemeen Dagblad".
That said, ANP can make mistakes too. Anyway, in the Department of Defence press release on this interception, there isn't any reference to an altitude of the unidentified a/c.
http://www.mindef.nl/nieuws/nieuwsbe...schepping.html
Cheers,
Aireps