Currently, Sections get applied to Boards and Timelines.
Sometimes that is just what you want, but often the universal choice isn’t right for some projects. A board may benefit from status/state-based sections, which can look odd in a timeline view where the benefit is being ably to see the sequencing and dependencies. Each viewpoint has its advantages.
A simple solution is to make the display by sections a selectable option on the project.
Hi @Graham_Robson, welcome to the Asana Community Forum 
Thanks for taking the time to provide this feedback! 
As it stands, Sections will automatically show up in your Timeline. As a workaround, you can sort your project by due date to temporarily be rid of Sections!
Hopefully this is something our Product Team can implement for Timeline in the future!
Hey Rebecca - Many thanks for the quick and empowering response. That’s a useful and workable workaround and achieves exactly what I need.
Hopefully, the power and advantages of different viewpoints are something that the Product Tam can build on further.