Contacts are not auto-populating in contact list column during update form submission


We have a sheet with tasks. One of our licensed users is sending update requests to other people (not licensed). This update includes a contact list column that they have to fill out enumerating people involved in the project. Our "My Smartsheet Contacts" is filled out correctly with all the names and emails including all the people that are in the company.

But for some reason, a person who is filling out update requests, do not see some of the names to be auto-populated in the column that are in the "my smartsheet contact" list.

Is there a way to auto populate the column with names during the update form submission for all the users? Why most of the names are appearing and others are not?