The double port:
Im not sure about this but heres a theory...
Background:
on my head on the exhaust side, I have an extra port as part of port 2 or 3.....this is blocked up during manufacture but i'm told that this is where EGR gasses would be taken from if this head was cast for egr.....
Theory:
one of the double inlet ports could be for coolant...like you said earlier..... to circulate (to warm up those parts of the inlet as soon as possible during warm up...<in the same way as the other water galleries in the inlet>)....the other part of the double port could be egr if it were fitted
may be you have a non-egr head with an egr inlet m/f?
rich