Why is the "message" parameter in eth_signTypedData_v4 of type string? Bug?

[inaridiy]

I have a question regarding the type definition for eth_signTypedData_v4 in eip1193.ts.
Is it by design that the message parameter is specified as a string type?
I was uncertain if this was an intentional choice or a potential oversight, hence I thought it best to bring this up in the Discussions section for clarification.

viem/src/types/eip1193.ts

Lines 1218 to 1227 in 2ffbb6c

	{
	Method: 'eth_signTypedData_v4'
	Parameters: [
	/** Address to use for signing */
	address: Address,
	/** Message to sign containing type information, a domain separator, and data */
	message: string,
	]
	ReturnType: Hex
	},

[inaridiy]

Upon further investigation, it appears that within libraries such as web3 and ethers, the message is converted into a text format in JSON before being invoked.
However, in the case of the EIP712 proposal and examples from Metamask, the message is invoked as an object as it stands, which is quite confusing.

Either way, does that mean it's strictly a string?