Chainline Question

I'm well confused by all this... If you have a flipflop wheel when flipping it Round to the fixed side the chainline should be the same. If not a proper 120mm fixed hub if you respace frMs and put a 120mm hub would improve chainline.

That is what I thought would happen. But looking at it with both cogs on, the fixed cog is closer into the wheel by a fair margin, 5mm at least I would very roughly guess (becuase I can't find my ruler) than the freewheel.