Halliday & Matthiessen (2014: 512):
In written English, the projection is signalled by quotation marks (‘inverted commas’; for the significance of double and single quotation marks see below). In spoken English, the projecting clause is phonologically less prominent than the projected: if it comes first, it is often proclitic (non-salient and pre-rhythmic, while if it follows all or part of the projected, instead of occupying a separate tone group, it appears as a ‘tail’, a post-tonic appendage that continues the pitch movement of the preceding projected material … .
The reason for this is that the main function of the projecting clause is simply to show that the other one is projected: someone said it. There is nothing in the wording of a paratactic projected clause to show that it is projected; it could occur alone, as a direct observation.