Issue Forms for Confluence uses the public rest interface to interact with Jira. Jira returns the name of the issue type in the language of the current user. It also returns the ID of the issue type. This ID is stored in the Issue Forms - create form macro.
The App Portfolio for Jira defines some fields, which we (partially) support since 2.4 (see also: https://aevolu.atlassian.net/browse/JINC-38 ).
Parent Link also belongs to these fields. This field uses a rest service to propose Jira issues.
The rest service requires the issue type so that it can return the appropriate parent for the issue type.
The name of the issue type must be provided in the default language of Jira. Unfortunately it is not possible to pass the ID or name in the user's language.
As we cannot determine the name of the issue type in the language of the system, the Parent Link field must be specified.