If it weren't BBC, I'd swear this article is paid placement. It is in the "Business" section, so maybe that section is like Inc. or Forbes or any other "news" magazine.

Anyway, in 2014, when the even happened (further implicating this being an advertorial) pretexting had been illegal in the US for 7 years already. I couldn't find any data on whether it's legal or not in EU/DE. (The event in question occurred in Munich.)

It's part of a series "exploring how technological innovation is set to shape the new emerging economic landscape". They do run some of these softer business features quite often. They have a regular one called "The Boss" which is usually a puff piece on some entrepreneur you'd never heard of. Sometimes they're quite interesting. This particular one is of fairly low quality. Everyone has an off day when they have to get some copy to their editor on a deadline

Maybe the fake journalist produced some ID/paper saying he was from the claimed news company, if so the police has grounds to arrest him for document forgery.

Pretending to be from a certain newspaper does not justify arrest, but he could have been taken to the police station for identity verification (possibly § 263 criminal offence of fraud according to the German Criminal Code)