confused api version

[tweyseo]

recently, i use v0.20 to kafka_2.11-0.10.2.1, when _fetch_api_versions, it retrun 35(UNSUPPORTED_VERSION), so i try V3 to V0 here, and V3 to V1 all return 35, but v0 return close, i check the server log and i saw Error reading field 'client_id': java.nio.BufferUnderflowException. then, i change > to >= here and server return the right 'api version response‘.
i was confused in two ponit here:
1.why fix the api_version for request to API_VERSION_V1 here @zz123er ?
2.why not the adjiust API_VERSION_V0 here @zz123er ?