Resolved! STM32G4 SVD files missing few EXTI-PR1 bits.
STM32G431K8 SVD file seems wrong. Reference manual (RM0440, February 2024 RM0440 Rev 8) show EXTI->PR1 bits PIF29,PIF30,PIF31 (Comparator 3,4,5 outputs). Fresch SVD file (STM32G4 SVD V2.2) missing these bits.