Putting aside the politics, this seems like a very poor decision. Historically, I believe most registering authorities have made great efforts to grandfather-in prior domains, for practical reasons apparent to most visitors of this site.
Additionally, shoddy treatment of 10% of current registrees will do nothing to increase the perceived value of an .eu domain. I also note that it appears the EU commission didn't even discuss the policy with the company that manages the .eu domain:
https://eurid.eu/en/news/ec-releases-communication-concernin...