Hi Luis,
'covers' may not be the correct phrase: The cells have gray sidelines only on the right and the lower side, not on the upper and left side: this is equivalent to a white line overlapping the left and upper cell frame lines. This is true for your two samples also and I understand that this may be the intended look. However, if table size is set to match the cell heights and widths, i.e. not showing a background, this results in the visual appearance of a double line, see the first post of this thread.
This double line is sort of irritating, but if it is the correct appearance I will get used to it 
Wolfgang