Yes you can definitely see the moire in the image without the filter where the back of the shirt is exposed. I think that the filters do a good job, even #8 and see that filter as being the best compromise, along with 5.6 being good too. #2 puts the image too out of focus.
From your test, I feel that the filters would work for almost everything I would encounter in architecture and interiors, but what about fine linen. That shirt did not give anywhere near the worse moire I have seen in images, do you know how they work for things like that.