In Project Blueprints, we are unable to use the rules to disable attributes if it is Rich Text (RTF/Large String), in the rules, you can not select any rich text large string. The documentation for blueprint and business rules does not say any restrictions.
Release : 16.0.3
RTF attributes not available for Business Rules is an expected behavior.
Following excerpt from Blueprint documentation.
When you select an attribute in the Conditions section, the following attributes are available: