Yeah, I've been wondering that, still wouldn't wouldn't explain it though as you can still sign players from e.g. Argentina on a pre-contract, and they're obviously not in the EU.
On the other hand, you can't sign Brazil-based players like that either(until a month before the end of their contract, but you don't even get that with the UK ones now). I guess it's just a different set of rules from country to country, even more so after Brexit.
On a side note, I've also noticed that the values of UK-based players don't decrease as their contract comes closer and closer to expiring, like those of all other players. Not the end of the world, but a bit frustrating when I had my eye on two players whose contracts were due to expire the next day and I couldn't offer them terms. Pressed continue and the next day they've been signed by other clubs before I had a chance to even offer them a contract. Extremely frustrating