I think the question is what these presenters may or may not also be doing behind the scenes - it's possible the newsreader is contributing to scripts or working on other projects in addition to the two BBC 1 shifts, which a NC presenter would be unable to do.
Interesting to hear Julia Somerville will be joining the Saturday bulletins, but she's already presented BBC Breakfast. Also does 'A BBC spokesman said: ‘We have a range of presenters, including Fiona Armstrong, Julia Somerville and Zeinab Badawi who regularly appear on the BBC News Channel', in addition to the Mail's claim about Carole Walker's criticism, suggest she's been dropped as a relief presenter? It would be a shame if she has, but I haven't seen her presenting in a while.
It's also worth remembering that, unlike Julia Somerville and Fiona Armstrong were hired specifically as relief presenters, the Mail seems to miss the fact that Zeinab Badawi is a key presenter on WN including regular stints reporting and presenting the continuity of 'Reporters'.
If that was going to be the case it would be a Sunday shift surely, giving her two days in a row off, rather than four on, one off, one on, one off?
All the Sunday shifts are taken though aren't they - Nicholas, Maxine and then either Annita or Clive. Suppose if they wanted Martine to do Saturdays and lates, then they would do better getting Tim on Monday rather than Friday lates. But then again Martine on lates may just be temporary