Which distinction between Form V takalluf and Form VI takhyīl is sound?

Seven Semantic Functions of Form VI (Tafāʿul): Reciprocity, Multiplicity, Pretence, Response, Equivalence, and Independent Uses

• Feigning always requires two subjects
• Takalluf occurs only in the passive past
• Takalluf stresses deliberate effort; takhyīl stresses feigned appearance
• They are necessarily identical