Trying to configure native signature with just last name but getting an error

Summary:

I am trying to configure electronic signature - native to use only last name (new in 23B). I set up the checklist integrators setup per the documentation (which is odd because I looked and my current checklist tasks that use native electronic signature don't have a checklist integrator setup at all but they all seem to try and validate display setting - so maybe something changed over time?)

I setup the checklist item as shown below:

But when I try and electronically sign the document (via my Checklist/Journey) I get this error:

status failed: You need to enter the name that matches the name we have in our records. (PER-1532291)