NiceTabular: Centering within blocks does not work as expected

I’ve got a problem while using the nicematrix package. For demonstration, I created this table:

There are two Block elements, filled with green color. As content for the blocks I used some symmetrical comparison lines which have a dot in the center.

These dots should be placed exactly in the middle of each block. But this is not the case as you can also see at the overhang on only side of the block. If the content would be centered in the block, there should be an overhang of same size on both sides.

What do I do wrong here and how can I center the content properly?

Thank you! 🙂

Here is the code for reproducing:

documentclass{scrreprt}
usepackage{booktabs}
usepackage{nicematrix}

begin{document}

centering
begin{NiceTabular}{*{4}{wc{20pt}}}
  & Block[c, fill=green!25]{1-*}{rule{10.0125ex}{1pt}.rule{10.0125ex}{1pt}} 
  Block[c, fill=green!25]{*-1}{rotaterule{4.04ex}{1pt}.rule{4.04ex}{1pt}} & xx & x(cdot)x & xx 
  & (cdot)xx & xx & xx 
  & xx & xx & xx
end{NiceTabular}

end{document}