Posting the solution here (credit to
@theDBguy) in case other people run into this issue. This code was implemented into the recordsource of the form:
SELECT [Pivoted Data].Process, [Pivoted Data].[Control ID], SimpleCSV("SELECT DISTINCT ASD FROM [Pivoted Data] WHERE [Control ID]='" & [Control ID] & "'") AS ASDs, Round(Avg([Pivoted Data].[Pass]),2)*100 AS AvgPass
FROM [Pivoted Data]
WHERE ((([Pivoted Data].Place)=[Forms]![Pass Percentage Form]![Place_combo]) AND (([Pivoted Data].Unit)=[Forms]![Pass Percentage Form]![U_combo]) AND (([Pivoted Data].[The_Date])=[Forms]![Pass Percentage Form]![Date_combo]))
GROUP BY [Pivoted Data].Process, [Pivoted Data].[Control ID], SimpleCSV("SELECT DISTINCT ASD FROM [Pivoted Data] WHERE [Control ID]='" & [Control ID] & "'")
ORDER BY [Pivoted Data].[Control ID];