How to prevent user from entering a custom name in the signature field / Default to name on account?

I am sending documents for signature using the Adobe Sign authentication method (meaning users must sign into the correct Adobe Sign account to sign). However, when a user goes to sign the document, they are able to enter a custom name into the signature field. This name appears underneath the blue signature line. Is it possible to lock this field to be the name of the user listed on their account?

I also tried using the Signature Block field vs the regular Signature field. This field includes an "email" line which is locked and cannot be edited by the user. However, I would prefer to use the regular signature field with a locked name.