.....incorrect use of a defining clause

Mr Boris Johnson, the Mayor of London recently said in a speech announcing a project to help underachievers in government-funded schools 
“There is nothing worse than seeing pupils full of potential slowly drifting into apathy." 
We can understand from this that it is acceptable for the pupils that are not full of potential to drift into apathy. I don't think he meant this. I think he was just guilty of sloppy grammar. If he wanted to portray himself as the saver of potentially pathetic juvenile souls he should have used the non-defining clause “There is nothing worse than seeing pupils, who are all full of potential, slowly drifting into apathy."  (ps - I don't actually know what drifting into apathy means, but it sounds like something you don't want to happen to young people). Using a non-defining clause in a sentence when speaking is a bit tricky, but the British politician can generally pull it off. However, with right-wing politicians, even when they use simple and compound sentences, it's not always clear what they mean when they talk about publicly-funded education. Most of them, like Boris Johnson, went to private schools, so only have second-hand information about the state system, fed to them by assistants who themselves went to private school.  Still, Boris Johnson is regarded as a jolly decent fellow so lets hope that he can get all those slackers to shape up and learn how to conjugate their verbs.