The effect AFAICS does not affect the original image size - it just distorts it - a bit like looking at an object through a lens - the object is still the same size the lens just distorts the image you see.
I see what you mean with that analogy. But Size/Position normally show the current size, with any effects applied, yes? For example, if I place a JPG on the timeline and zoom in to 110%. Width and Height will now be 10% higher. Or if I apply 3D distortion, the size display will change. Etc. The original image hasn't changed in those cases either, but the result of the effect has changed its display dimensions.
So why don't these New Blue effects obey that rule?
It is probably because the plugin works in its' own window and does not interact or comunicate with the Size Posn. window. If for instance you use the New Blue colour correction tools, you would not expect to see that change the MEP colour effects sliders and hue wheels.
AFAICS, and I think this is another way of putting what Peter said, the effect is an 'invisible' overlay ie what you see in the preview monitor is the result of the image being preprocessed through the filter before it is displayed.