@CSB You're saying 2 lines there that's not related to each other anymore.

1:
Spain allows entry of all EU citizen. Yes, that's normal because of Schengen acquis, which is basically a contract that EU-members have made with each other to allow for freedom of movement within the EU.

2:
Spain refuses entry to Brits who don't own residency permit. Yes, and? Brits aren't part of the EU anymore. So it's up to Spain how to deal with them, they don't have that fun contract.