Today my (cheap) USB microscope came in. So I could finally see what was going on.
I used the microscope to make photographs of the stones at a magnification of 400x. Here they are.
The 400 grit stone:
The 600 grit stone, already smoother than the 400 grit:
The 800 grit stone, definitely smooter than the 600 grit:
And finally the 1000 grit stone, about which I had my questions:
To me the 1000 grit stone looks (a tiny bit) smoother than the 800 grit stone.
Nothing wrong with QC at Wicked Edge. Thanks, Clay!