Why did ST assign a pin to their official board and software when it can't even be configured in CubeMX?

[jmh8231]

Looking at the Ethernet PHY circuit of the STM32H735G-DK, the MCU and MAC are connected via the RMII interface, and a pin named "RMII_RX_ER" is connected to the MCU.

However, if you configure it for RMII in CubeMX (version 6.18.1), this pin does not activate normally. If the user manually activates it with the mouse, the pin is marked in yellow, meaning the function is not properly enabled 

Therefore, I checked the official Demo FW located in STM32Cube\Repository\STM32Cube_FW_H7_V1.13.0\Projects\STM32H735G-DK\Applications\LwIP\LwIP_TCP_Echo_Server\STM32CubeIDE, and even there, the pin is configured as GPIO_AF11_ETH.

 

I am curious why it was designed and developed this way when it only gets configured but doesn't actually function. Is it just missing from the ETH group in the CubeMX DB? Or is it originally an unsupported feature, but ended up like this because an existing circuit design was just recycled?

[waclawek.jan]

Now I’d like to add that I am not ST nor Synopsys insider and from the available documentation it’s not clear, if asserting ETH_MII_RX_ER signal at PB10, while the ETH MAC is configured in RMII mode, does or does not set the RE bit within the status bits of writeback Rx descriptor (in RDES0 in the original in ‘F4, in RDES3 in the newer one in ‘H7).

Oh, and I am by no means associated with CubeMX.

JW