When using the Collapsed Topics format with "All sections on one page" layout, Section names, regardless of theme, are always centered and sized at .9 em.
Section names should pick up the styling from the Theme in use.
Is this happening because Section Names in Collapsed Topics lose the H3 tag? (In other course formats, the text for section names is H3. In Collapsed topics the Section name looses the heading tag.)
Note: If using "Show one section per page" layout, this is not an issue; Collapsed Topics behaves the same as other formats. On the Main course page, Section names do pick up Theme styles and are H3s, and on Single section pages, Section names are centered (as needs be) and again, pick up theme styling.