I think that in Conditional visibility you can only access attributes of the object in the surrounding dataview, Treatment in your case. You can not access attributes over an association such as patient.
Hope this helps,
As Andrej already noticed, it is not possible to compare attributes over association when using the conditional visibility expression.
For me, it helps to create a surrounding Data View around the tab container you're using (Patient over association). In that case, you can use the patient object for your conditional visibility. I see that you are using an over association data grid inside the tab container, so you may need to add a 'Return Object' microflow in order to use the data grid as you are using it now.
Hopefully this helps. If you have any additional thoughts, please let us know.