CSS Display says

The inner display of a replaced element is outside the scope of CSS.

I'm not sure if this means that:

1. Replaced elements have an inner display type set to some value which is not defined by CSS Display because it's outside the scope of CSS.
2. Replaced elements don't have an inner display type because how the contents of a replaced element are laid out is outside the scope of CSS.
3. Whether replaced elements have an inner display type or not is outside the scope of CSS.

The difference matters because in the glossary there is this sentence:

Any inline-level box whose inner display type is not flow establishes a new formatting context of the specified inner display type.

With (1) it seems clear that the condition holds, so an inline-level replaced element would establish a new formatting context. But I think this should not be imposed because it's outside the scope of CSS. With (2) or (3) it's not much clear whether the condition holds or not.

Anyways, I don't understand what that sentence is doing in the "atomic inline" entry, I would remove it. Does not seem much related other than atomic inlines being inline-level. And is kinda pointless, given that all the non-replaced non-layout-internal inner display types other than flow seem to generate some box which establishes a new FC, independently on the outer display type.