Tag implication: :o -> open_mouth

The :o tag's wiki states:

:o is:
Circle-shaped mouths of all sizes.
Only widely open mouths should use the open_mouth tag.

The open_mouth tag is defined currently as:

open_mouth is:
The mouth being open, not closed.
Only use when sufficiently open to (theoretically) see inside.

Is open_mouth like :o defines it, and requires a specific size or is that something that is inaccurate? Right now open_mouth, as far as tagging goes, it being applied regardless of size.

There are also some images where white is used instead of an inner mouth coloring (examples: post #1634394, post #1029194, and post #1027095). Does that qualify as open mouth or is it closed (as its likely white due to teeth), and shouldn't be tagged open_mouth? If it doesn't count as open_mouth, does it still qualify for :o, since it still has a circular shape?

Also, post #1012304 was under :o, is this supposed to be under the :o tag or is it incorrect? Similarly there post #1858649 which is more of puckered lips.