They state that if a sender wants to ensure that the recipient can remove the covenant, they may request a signature of a challenge string from the recipients. However, ZmnSCPxj notes that the recipients have the option to destroy the private key after providing the requested signature.Additionally, the recipients have the ability to refuse to cooperate with signing using the taproot branch, which would result in spending via the OP_CHECKOUTPUTSHASHVERIFY branch instead. It is important for both senders and recipients to understand these options when dealing with covenants in transactions.Overall, ZmnSCPxj provides valuable information regarding the intricacies of removing covenants in transactions and the various options available to both parties involved.