Is "required_signatures" parameter always be "1" ?
Not always:
{
"name": "required_signatures",
"type": "INT64",
"description": "The number of signatures required to authorize spending of this output"
},
There's multisig transactions that require n-of-m signatures so according to the above the value of "required_signatures" will depend on whether it's a multisig transaction or a regular one with only a single required signature.