GlyphsViewer App not displaying component glyphs?

GlyphsViewer App on my iPhone SE/iOS 13.5.1 does not display component glyphs, instead the little triangle »no base glyph« is shown, while the preview panel in GlyphsApp [1339] shows everything correctly.
Interestingly this is only the case for all the instances from light to black, whereas thin, which is my lightest instance, works as expected on the iPhone.
Is this normal behaviour or can I change this somehow?