This does not match the results from 5 minutes of googling, not for individuals at least. What is being taxed is the shares you're holding, as if you're selling them, which results in a tax on their increase in value compared to when you've bought them. [disclaimer: I just did a quick search on this, I'm not a tax consultant or lawyer.]
I haven't looked for the regulations on companies moving their headquarters away from Germany. It's possible those rules are the above, and the author confused them with the rules for individuals.
Either way, if the author believes they're right, they should dig up some citations. There are none in that article. Is this based on advice they've received? Did they do their own research? Are they a tax consultant or lawyer? 13.75 is a very "spottable" number, how about a link to the law that has that number?
https://de.wikipedia.org/wiki/Wegzugsbesteuerung
Essentially, it assumes you sell your assets at market value and taxes the difference to your expenses for it.
Is that... the first recorded instance of an AI committing suicide?