When you edit collection from an article (create a new collection with the article) the title/description are not styled as they should.
There's a .collection-header in the CollectionEditorOverlay that needs of the styles that are on the module ext.gather.styles which seems to be loaded via addModuleStyles only in the special page.
Not sure about the solution. Either copy the collection header styles to the collection editor styles, or split the module to smaller ones and load the collection-header twice on special pages when editing a collection. For that trouble though, copy&pasta of those ~6 lines of less seem the most straightforward solution.