For ages now I would amend a drawing in SketchUp and then open the Document Setup box in Layout, select References and then the file that I want to up date in Layout.
Drawings changes are now being updated in Layout automatically. I must have accidently checked something.
Normally that only happens if you open the SketchUp file from LayOut. That gets LayOut to watching for saves in SketchUp. If you don’t want that to happen, just open the SketchUp model directly, not from LayOut.
And if you don’t want viewports to update until you click on the Render button, untick the Auto Render box in the SketchUp Model panel.