Currently, the display name for Form fields is not updated on existing Forms that are linked to the issues. But only updates are applied to the Forms while creating a new issue.

Replication Steps:-

1. Create a Form with Labels/field names.
2. Associate it with the Request type.
3. Create a new request where the Form is associated.
4. Now come back to the form and update the label/field names, this will not reflect on the existing Forms that are associated with the requests