It isn't a good policy and if that is one of the best ideas of the EU then they have failed as a political project.
1. Corporations are exactly the tool we use to work out what trade offs of cost v. standardisation are best. Everyone is going to claim victory for a bureaucratic committee then a few years down the track we'll discover technology moves on and the regulation is force people to make stupid choices. Removing the flexibility to adapt at the forefront of technology is going to turn out to be foolish in hindsight. These devices aren't even 20 years old and the EU has already decided to start fossilising the tech.
2. There is a decent chance that this will corrupt the USB standard itself. We're already seeing the bizarre profusion of naming [0]. If there is an incentive for corporations to create incompatible things that are all named "USB-C" they may well manage it. Calls to mind the OOXML vs ODF format wars.
3. This is a total waste of political attention. I suppose now we know how the EU ended up in such a catastrophic posture with their energy policy. Their best and brightest were back-seat-driving iPhone design. Thank goodness for the Europeans, they may not have reliable power but if they did they won't have to search around for the right cable. And if we need to send phones into the land war, we know what adaptors to send with them!
[0] https://en.wikipedia.org/wiki/USB#Naming_scheme