Using a parameter within a calculation returns nulls when using the connector "Other Databases JDBC"

Hi. We recently moved our data to Redshift Serverless, in doing so experienced connection issues. The solution AWS proposed is to use the "Other Databases JDBC" connector. This does fix the connection issue but Ive noticed when I use a parameter within an IF statement as a filter it returns NULLs. The same parameter/calculation worked fine when using the redshift connector.

I note that Tableau says "some" features wont work with this connector, does anyone know if this is one of them?

Thanks Tash