!important required to override inline width and height styles on embed iframes. :-/

apostrophe-2/css/blocks.css

@@ -81,8 +81,8 @@ p.has-drop-cap:not(:focus)::first-letter {
 	left: 0;
 	bottom: 0;
 	right: 0;
-	width: 100%;
-	height: 100%;
+	width: 100% !important;
+	height: 100% !important;
 }
 
 .wp-embed-aspect-1-1:before {