On the face of it I’d agree with that, but my son, a 30 year resident of Germany and a German citizen for years now, came over for a visit just before we finally left the EU.
I saw his passport in the spare bedroom, and it said Bundesrublik Deutschland on the front, with Europaische Union on it as well.
I asked him where his U.K. one was, he said that it had expired some time ago.
I said that surely he could have renewed it at the U.K. Consulate in Hanover, some 100 km from his Bielefeld home.
He said that that was where he’d renewed it last time, but Germany wouldn’t recognise dual citizenship with U.K. when U.K. finally came out of the EU, so he didn’t bother.
I asked if that meant that he was no longer a U.K. citizen, he said that he might be, but didn’t care much really, he could go anywhere in the world with his German passport, including U.K., so what was the big deal?