My take would be that this is because one person is looking at Monday/Tuesday where indeed the 12z GFS Is a big improvement on the 06z. But the second person is moving onto Weds next week and it's back to westerly zonal weather on the 12z GFS, whereas the European models are suggesting (along with the constant anomaly charts that don't swing wildly like every run) that mid week next week will be a blocked pattern with continuing cold across the UK.
So, it is both looking much better, but then a 'horror show'!