Description of leaf /routing-policy/policy-definitions/policy-definition/statements/statement/conditions/match-protocol-instance/config/protocol-name currently states (emphasis mine):

The string must match one of /network-instances/network-instance/protocols/protocol/identifier in the local network instance.

However, leaf protocol-identifier in the same container already matches /network-instances/network-instance/protocols/protocol/identifier, which is one part of the key of the enclosing collection, the other being name:

container protocols {
  description
    "The routing protocols that are enabled for this
    network-instance.";

  list protocol {
    key "identifier name";
    // ...
  }
}

Everything points to idea that authors wanted protocol-name under match-protocol-instance to point to the name, not identifier. We also have type mismatch otherwise, names being strings and identifiers being equivalent identityrefs. Therefore, the description needs to be corrected by changing the word identifier to the word name.