Lack of transparent supply auditability is a feature not so much of zk-snarks but of Confidential Transactions, which use Pedersen commitments to obscure amount

Lack of transparent supply auditability is a feature not so much of zk-snarks but of Confidential Transactions, which use Pedersen commitments to obscure amounts. Knowing the discrete logarithm of just one particular point would completely break these commitments and all cryptocurrencies based on them, by allowing undetectable inflation. They thus require complete confidence in the computational hardness of the Elliptic Curve Discrete Log Problem.