GET /dag/car Request parameter question

[qianhh]

GET /dag/car
Request

{"ReqId":"00c1d646-7b06-445f-9162-1966c670f37d", // UUID for the request -> used for referencing, logging and debugging. Mandatory.
"Root":"QmfMYyn8LUWEfRXfijKFjBAshSsPVRUgwLZzsD7kcTtX1A", // Base64 string encoding of the cid byte array. Mandatory.
"Selector":"", // Base 64 string encoding of the selector byte array. Optional and can test without this for now.
"SkipOffset":0 // Skip offset for the CAR to download. Optional. 
}

Why is Root in the request parameter here Base64 encoded? Wouldn't Cid's built-in String function conversion be simpler and more general? Also, Root in this example is not Base64 encoded.