Voluntary disclosure sounds as if it undoes the secret ballot.

Just a reminder: the secret ballot is secret to protect those, whose genuine vote would otherwise be manipulated (/forced/extorted/...)

Not every individual voter might need that level of protection for themselves.

But every individual voter requires this level of protection for the whole process.

Phrased differently: for some, anonymity in voting is nice. For others, it is necessary to get their genuine vote. For democracy to function, we need everyone's genuine vote.

Thus: we need voter anonimity that cannot be rescinded by the voter - nor by anyone else.