Security policy rules control network traffic based on its source and destination security zones. The three rule types are defined as follows:

• Universal: This rule type is the most comprehensive, applying to all traffic combinations for the zones specified. It matches both traffic between different zones (interzone) and traffic that stays within a single zone (intrazone).
• Intrazone: This rule type specifically applies to traffic where the source and destination are within the same zone. It does not apply to traffic crossing zone boundaries.
• Interzone: This rule type applies only to traffic that moves between different zones, meaning the source zone is different from the destination zone. It does not control traffic that originates and terminates in the same zone.

Palo Alto Networks. (2023). PAN-OS® Administrator’s Guide, Version 11.0. In the "Security Policy" chapter, the section "Security Policy Rule Types" defines the universal, intrazone, and interzone rule types. It states, "A universal rule... applies to all matching interzone and intrazone traffic in the specified source and destination zones." It defines an intrazone rule as applying to traffic "where the source and destination zones are the same" and an interzone rule as applying to traffic "where the source and destination zones are different."

St. Petersburg College. CNT 2402: Network Security and Countermeasures (Firewall). Course materials on firewall policy configuration explain that policies are differentiated based on whether they control traffic within a security segment (intrazone) or between different security segments (interzone), which aligns with the logic presented in the question.