The valve has two positions. One is "Straight through" if by Reversing the flow you mean the valve handle was to the left side of the valve body and is now on the right. that will still work the same
However the "alternative position will connect the antifreeze suction line to the tank line not to the pump inlet so that will cause an issue
if by reverse you mean you swapped the tank side line with the antifreeze line. No it wont' cause an issue just make sure the valve points to the line you want to suck from.