The world’s largest asset manager has filed for an amendment for its Bitcoin exchange-traded fund (ETF) following widespread investor concerns over Coinbase’s onchain settlement practices. BlackRock has filed an amendment to require Bitcoin (BTC) withdrawals within 12 hours from the ETF’s custodian, Coinbase, according to a Sept. 16 filing with the Securities and Exchange Commission (SEC). BlackRock wrote in the filing: “Subject to confirmation of the foregoing required minimum balance, Coinbase Custody shall process a withdrawal of Digital Assets from the Custodial Account to a public blockch…