Some anecdotal data on the font. It appears to be part of macOS's "supplemental" font list. On a macOS 12.6 fresh install on a VM, I don't see it installed. But it is listed in `Font Book` as installable. On the VM, I never previously ran the `Font Book` app or elected to install any extra fonts. After upgrading it to macOS 13.7, I see it present at `/System/Library/Fonts/Supplemental/STIXTwoMath.otf` so it appears to have been installed as part of upgrading to macOS 13. Some articles online say that starting with macOS 13, supplemental fonts are always installed and can't be removed, only deactivated.
Bug 1902570 Comment 13 Edit History
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Some anecdotal data on the font. It appears to be part of macOS's "supplemental" font list. On a macOS 12.6 fresh install on a VM, I don't see it installed. But it is listed in `Font Book` as installable. On the VM, I never previously ran the `Font Book` app or elected to install any extra fonts. After upgrading it to macOS 13.7, I see it present at `/System/Library/Fonts/Supplemental/STIXTwoMath.otf` so it appears to have been installed as part of upgrading to macOS 13. Some articles online say that starting with macOS 13, supplemental fonts are always installed and can't be removed, only deactivated. If we need a definite answer, we can reach out to our Apple contact.