If they hold that stance, the graph should not use ‘Europe’ when they essentially mean ‘EU member nations’, especially if they omit the UK for the reasons you state as the UK is a part of Europe.

Edit: not sure how difficult this is to understand. Europe is a continent, which includes the UK. The chart says Europe, not EU, whilst omitting a country within Europe.

Why do these European charts omit the UK?

We left the EU, not the bloody continent.