Steps to reproduce:
Create a space and activate the Scroll Help Center theme
Place a Viewport redirect macro on the space home page and save it.
Switch to the Viewport view of the home page
The Macro is skipped and the first paragraph after the macro is displayed as the page description.
$page.description (contentplaceholder) is pulling in content at the top of the page. If this content contains a Viewport redirect macro, the macro is executed and one is redirected to the defined URL