why the grid no longer shows up when setting the grid size to less than 4 pts?

When making grid size 2pt, by editing the file

styles/basic.styles

and adding these 2 lines (thanks to Ernest Menville reply)

<gridsize name="1 pts" value="1"/>
<gridsize name="2 pts" value="2"/>

Now when I open new drawing, I can see the 2pt and 1pt in
the menu. I select 2pt, but now the grid itself is no longer visible.
(F12 or by clicking on the grid button on the menu).

The grid become visible only when the grid size if >= 4pt.

Is this how it is supposed to work? I need to see the grid,
but also make the grid spacing smaller than 4pt. May be
due to small size, it is not possible. Just thought to ask.

Using 7.1.8 on windows 7.

thanks,
--Nasser