https://bugs.winehq.org/show_bug.cgi?id=56658
--- Comment #2 from Sagawa sagawa.aki+winebugs@gmail.com --- Despite our comparison to 'dflt'[1], the font file and OpenType specification[2] uses 'DFLT' for default script tag. This is the cause of Kosugi font issue.
While trying out another Google Font, I noticed that KaiseiOpti[3] had more complicated problems. The GSUB table in the font contains the kana and DFLT script tags. However, the vert/vrt2 feature is not listed in the kana script. Instead, it's in the default script. Therefore, we need to fallback to the default script in this case.
[1] https://gitlab.winehq.org/wine/wine/-/blame/wine-9.8/dlls/win32u/font.c?ref_... [2] https://learn.microsoft.com/en-us/typography/opentype/spec/chapter2#slTbl_sR... [3] https://fonts.google.com/specimen/Kaisei+Opti