SwiftUI - MacOS - VSplitView breaks Xcode's Preview

I have a not-too-complex SwiftUI layout for MacOS. When I add a VSplitView, Xcode's Preview pane breaks a bit, in that the blue highlight squares no longer align with the actual elements. It's as if the highlights are using a version that's scaled by 0.3x or so. Changing the VSplitView to a VStack restores correct behavior. Is this a known ?