Got the right answer from Jonathan Drummey! Thank you Jonathan.
Instead of loading up the IF calc, create an additional calc that use the parameter to ID when Shared Services or IT Org is selected, like this one:
CASE [Alternative Hierarchies]
WHEN “Shared Services” THEN IIF(NOT ISNULL([Shared Services]),1,Null)
WHEN “IT Org” THEN IIF(NOT ISNULL([IT Org]),1,Null)
Make this discrete and filter for 1. I’m using 1 and Null instead of a Boolean True/False because Tableau won’t let us return Booleans from CASE or IF/THEN statements.