According to everything that I read and been reading, Stealth planes don't use "gap-fillers" only has you mentioned but complete skins which covers complete surfaces, at least the F-35 does.
You've been reading the wrong things then.
Besides, either the link above or the pictures posted by Hasp clearly shows that even older Stealth aircraft such as the F-117 had complete Stealth coating/skin which cover not only gaps but complete surfaces.
Old news. All those aircraft use shape primarily, the F-117 needed a lot of RAM coating, the F-22 and F-35 undoubtedly use RAM-paint as well, as do other fighters today ... and they also use gap-fillers. The main stealth concept is shape, not paint. Paint's the icing.