Dual PS-ON signals connected to the BTT Relay V1.2 board

[Wombat37]

This is not a bug issue but more of a question.

I've installed the BTT-Relay-V1.2 on my BTT-E3-RRF system running RepRap and all is working well. The PS-ON is connected to the Relay board 3.1 connector. M81 turns off the PSU and a switch on the RESET connector turns it back on. I've connected up a 5V line to the electrical short protection Connector 3.2 and, while I don't know how to test it safely, it doesn't stop operation.

One valuable application of this product could be to power-down the system in the event of a critical fault (e.g. loss of temperature control of one of the heated zones). RepRap doesn't support this but I note that the TFT display firmware does provide support for the hotend temperature range. My BTT-TFT35-E3 v3.0 display also has an unused PS-ON connector on the back of the board.

My question relates to the (apparently) unused and undocumented 3.3 connector on the V1.2 board. What is it and what does it do? Can I connect a second PS-ON signal from the TFT to the 3.3 connector to trigger a PSU power-down in the event of a hotend temperature failure? Failing that, can I connect the two PS-ON signals in parallel to connector 3.1 to achieve the same thing?

Any feedback would be appreciated.