glibc might start selecting optimized functions/libraries based on the AT_PLATFORM architecture string identifier. We currently adjust the AT_HW_CAPS[2] based on the actual instructions we support (see setup_client_stack in coregrind/m_initimg/initimg-linux.c), but in the future we might also want to adjust AT_PLATFORM (e.g. change power10 -> power9 or z15 -> z13). The current proposal is on the glibc mailinglist: https://sourceware.org/pipermail/libc-alpha/2020-May/113757.html
To clarify that the libc-alpha posting is not a proposal, it is a description of the status quo. The proposal (buried in there) is to move towards AT_HWCAP-based selection exclusively, but that has not been implemented yet, and would not affect the legacy directory selection logic at first.