That's interesting, thanks for sharing -- but that linked article is from 2016, so not sure it can refer to the GDPR DPO.
What DPO is that case about? Is it under the DPD (which GDPR supersedes)? If so, what does the DPD say about conflicts of interest and DPOs?
If the law that this case was prosecuted under has as loose a definition as the GDPR, then you're right that this implies German regulators could well enact the GDPR under that interpretation too.