Github user bbende commented on the issue:
https://github.com/apache/nifi/pull/2913
Actually, I take back my last comment, I now see where the value is
obtained and it does have the logic:
```
String propertyValue = propertyDescriptor.isExpressionLanguageSupported()
?
context.getProperty(propertyDescriptor).evaluateAttributeExpressions().getValue()
: context.getProperty(propertyDescriptor).getValue();
```
Sorry about that.---
