I am experiencing this too, but I am using Flutter / Google fonts package from pub.dev, so not a native codebase. No accessibility settings enabled on my phone. VERY sizable differences between the fonts based on iPhone 12 mini on simulator vs. on TestFlight downloaded on my ACTUAL 12 mini (with no settings). Didn't show up using flutter run --release, so this might be something that happens in the .ipa / binary creation?