This is not a problem with Intuit or DocuSign.  It is inherent in the design of a US-centric system.  And at the early stage of the rollout, service providers took a very conservative approach and shied away from offering alternative authentication methods.

As you may be aware, Intuit and DocuSign have added a new authentication method based on Access Code, which some other providers have already been offering for some time.

If push comes to shove, you client can always resort to signing the form and returning it as an image file.

https://proconnect.intuit.com/support/en-us/help-article/manage-integrations/authentication-methods-...