Exceptions exist, that's what makes a 'general rule' general.
The UK is a member of the EU which means any citizen of another EU country has the right not only to enter but to work in the UK. Other exceptions also exist, so what. I think the point is clear.
Even the 'exceptions' have exceptions. For example, a citizen of an EU country who would normally have the RIGHT to enter can be placed on an 'exclusion list'. Some UK football supporters are regularly banned from entry to some other EU member countries for example.
Don't nitpick what isn't important. The only people they CAN'T refuse entry are citizens of the country GUWonder.