Chat Arena version of fastchat-t5-3b-v1.0 provides more refined answers than standard Huggingface model.

Hello - I notice that the chat arena version of fastchat-t5-3b-v1.0 provides quite different answers from the model compared to when it is downloaded manually and run using fastchat.serve.cli --model-path lmsys/fastchat-t5-3b-v1.0. What is the reason for this difference? Are there any special prompt templates or prompt tuning that gives the chat arena version its better responses?