Not a very scientific statement, because no one knows what you are testing. And if the meter can't see the difference you need to return it as faulty. There is a huge difference between the the Single and the Twin in band D. And you talk about daily fluctuation as if it is nothing, but that is not true either. For a lot of people it is the difference between viewing and not viewing, and if the change from one of those LNBs to the other gives that effect, for some it will be enough to better their viewing from part time to full time.
That's not what I wrote.
I do not claim to conduct scientific experiments, I just compared a Single and a Quad, and found very little difference.
(I did use a ProMax TV Explorer II+, which was calibrated only a year earlier, and otherwise sees very little use.)
I made no comparison between the single and the dual, indeed I wrote I have no duals to compare with.
And finally, I commented that the difference I measured was so little, that you might see this variation between different LNBs of the same model. OR, differences that could be due to daily fluctuations, as I did not measure the two LNBs at the same time of day.