Below is something I posted in March-2017 that illustrates the zoom scales at which we transition to the smaller grids. As you can see you need to be in pretty close to have the grid change.
That said, when the grid didn't change, we received complaints that the movement was 'choppy' as it jumped at larger increments. I have logged a suggestion based off of your requests to have an option for the grid to stay at 1/8" with the understanding that the cursor movement could be difficult at close zooms until it transitions to small cursor with no grid.
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Posted 22 March 2017 - 12:30 PM
We have introduced a new dynamically scaled mouse grid that will scale down as you zoom in closer. This behavior is evident without needing to drop to the small cursor.
The typical grid size is still 1/8" which will transition to 1/16" and then to 1/32" when zoomed in very close. This will help when drawing in small spaces while staying within a grid size that still aligns to the 1/8th inch grid.
Below are some examples of the zoom scales at which we transition to the smaller grid sizes.