How is Magento\Vault\Model\Method\Vault::assignData() implemented and used?

Context: How are the payment data assigned to the Vault payment method instance on an order placement?

Implementation

This event is handled by the Magento\Vault\Observer\PaymentTokenAssigner::execute() observer.

The $this->getVaultProvider()->assignData($data) for the Braintree Vault calls the Magento\Payment\Model\Method\Adapter::assignData() method.