We have a design with CYPD4155 where SCB4 is connected to a host processor, and SWD nor any other I2C ports are connected. Will the factory bootloader on this part accept programming on SCB4?
No. It cannot be programmed. Since CCG4M is pre-programmed I2C boot from factory. The I2C boot is assigned to SCB1. So that the factory bootloader on this part cannot accept programming on SCB4.