Hello,
There is no issue with how you set up your Record Formatters. Instead, this seems like a bug; the query you created should display the Determiner field as it appears on the Determination form. I have written up a bug report on GitHub to notify the developers of the issue: Queries not showing aggregated group members configured in Agent field format · Issue #5363 · specify/specify7 · GitHub.
If you would like to avoid this issue, there is a “Determiners” one-to-many relationship that can be rendered as a subview on the Determination form instead of the Determiner field. This relationship allows you to add multiple Determiner agents without the need to create a Group.
Here is what you might add to your Determination form definition:
<row>
<cell type="subview" viewname="Determiners" id="9" desc="Authorization" name="Determiners" colspan="12"/>
</row>
You can learn more about editing forms here: Editing Forms in Specify 7.
Thank you for bringing this to our attention!