“It doesn’t necessarily increase the security of the product, but it does make introspecting the device and reverse engineering the device a whole lot more difficult.”
Red Balloon Security built a robot from a $500 AliExpress CNC machine, an FPGA reader and an ESP32 that freezes DDR3 chips one at a time and lifts the decrypted contents out. The whole rig costs around $2,000. Vendors disable JTAG, encrypt firmware and use BGA packages, and the plaintext still sits in RAM. Locking out the debug port only locks out the researchers with small budgets.