When using a full-page layout.
When having a flyout-menu in the west position (left position).
The flyout is blocked by the width of the left layout border (the border between the left/west and center positions).
This feels unnatural.
As a user I would expect the flyout to overlap the border into the center content area.
I wouldn't feel that I should have to widen the left layout to accommodate all the possible flyout widths.
From a user perspective, the menu to be functional should occupy minimal width by default - just the width of the primary menu items.