,1990 Olds 307 V8 Heater Valve

I have NOS Heater Valve 2250236 and it has a small female threaded connector on top that my blown original doesn't have. This is the replacement valve listed in the original part book. What goes on that connector. I know the heater hose goes on the big port and the vacuum line goes on the vacuum port but what goes on the threaded female?

Wild guess. Is it the ‘outlet’ for bypassed coolant? To allow coolant to keep flowing, instead of just pushing up against a closed valve?

Apparently they consolidated valve types and that port is only used if you have auto CAC. Nothing attaches to it on mine and the system works fine now that it is installed and no more coolant leak.