The last paragraph quote that you pasted from the manufacture is what I am referring to. If you use the 10 x 20 inch carbonized rubber Mat without the optional cover, but instead with wearing light cotton socks, you will get a ground. Also again the rubber mat if used in your bed, it will make a conductive ground connection through very light cotton PJs or socks.
The Earthing Sheet products will Not do this, as they are not as intensely conductive it seems as the rubber mat. The problem with the mat though is that it is small for the bed. But I do know many people using the mat only in the bed with great results.
There is product tester also which will indicate if there is flow from the product into the person's body which also verifies that it works with some light clothing, but the best results is how well you sleep and feel in the morning.