BoringSSL implemented this in https://boringssl.googlesource.com/boringssl/+/858a88daf27975f67d9f63e18f95645be2886bfb
This allows a server consumer to specify multiple cipher suites at the same level of preference, so the server can enable SSL_OP_CIPHER_SERVER_PREFERENCE, but also take the client's preferences into account when selecting one of several ciphers that are all equally preferred.
The upshot, as described in that BoringSSL commit message, is that the server can prefer AES-GCM and ChaCha20 equally. Android devices without hardware AES support put ChaCha20 first in their suite preference list, so with this feature, the server could select AES-GCM for clients with hardware support and ChaCha20 for ones without it, which optimizes performance for both cases.