[Pharo-dev] Job: from Exceptions to Announcements?

Hi, I am looking into SystemProgressMorph and I found this flag in several methods: self flag: 'When we go from Exceptions to announcements, delete this and use show:from:to:during:'. I'd like to know more. I see that Jobs are implemented with both exceptions and announcements... what is the idea? to remove the exceptions and use only announcements? Thank you for your help, Martín