The granularity is up to each user, none is enforced.
I personally just stick to base domains usually. When a site is broken, allowing one or two 3rd-party base domains is often just enough to fix it.
If you want to go subdomain-granularity, this is your choice -- it's not forced on you. Some even go as far as subdomain/type (the cells in the middle).
I think the bigger problem is that it exposes the grid from the word go.
I myself though i had to enable each sub-set individually until i took a closer look at the behavior when clicking certain ui elements (that as i recall were unlabeled).
Noscript on the other hand only present a list of domains, though one can enable sub-domain granularity in the options (never felt the need).
I personally just stick to base domains usually. When a site is broken, allowing one or two 3rd-party base domains is often just enough to fix it.
If you want to go subdomain-granularity, this is your choice -- it's not forced on you. Some even go as far as subdomain/type (the cells in the middle).