Return Button UI Error Bug - Embed API Viewer Customization

Using the Embed API in Light Box mode and using the viewerConfig to set the ExitPDFViewerType button customization to 'Return' (rather than the default 'Close'); The return button has no margin/padding on the left side.
This is clearly an error/bug as the images for that customization feature in the API documentation does show the correct spacing on the left-hand side (see attached image).

Adobe bugfix required, as the Light Box embed option is an iframe so I can't use CSS or custom JS to add the correct padding.