Font families missing from the font list when running with FreeType on Windows

We have been battling with this issue since Qt 5. It's reported here in our repo but it's come up long before that, and we now find it persists all the way to the latest Qt version. I think I've finally found the most minimal reproducible example for this.

To reproduce, just run on Windows the "Font sampler" example that ships with Qt. When running with native font engine, I see all the installed font families, see in particular "Miller Text". When running with Freetype, "Miller Text" disappears (see the screenshots attached)

This seems to be a Windows-specific issue. On Linux, "Miller Text" is still visible even if Linux also uses Freetype. We have not been able to understand what it is about a specific font that causes it go missing from the list. Miller is one font that has this problem (Miller font files are attached). Another font that had this issue was Nepomuk.

This is kind of a big deal for us, because we need to stick to FreeType as it produces a much better rendering than the native engine when rendered with QPainter via QQuickPaintedItem (which is also an issue that I'll probably report separately). At the same time, it's a bit embarassig if our users install custom fonts but can't use them in our program.