MediaWiki automatically makes a warning for all transclusions with duplicate arguments and displays it above the whole preview and a horizontal line. It was introduced at phab:T85352 and uses MediaWiki:Duplicate-args-warning. Example: "Warning: Page using Template:Infobox website with unknown parameter "Video Personality" (this message is shown only in preview)."
When previewing the same article within AWB, the same message is not displayed allowing the introduction of errors (although usually not very consequential ones) that are easier to catch with normal Preview mode. This is inconsistent and I believe AWB should show these warning messages as well.