Hardened Android standard C library. Some of the past hardening has not yet been ported from Marshmallow, Nougat and Oreo to this Android Pie repository. Most is available via archived tags in https://github.com/AndroidHardeningArchive/platform_bionic (check both the most recent Oreo and Nougat tags).
Why do you think that https://github.com/GrapheneOS/platform_external_Camera is a good alternative to platform_bionic