The patent describes not just "slotting in", but one way in particular. Note that if you were to "slot in" ANS into the current AV1 codebase, for example, it wouldn't actually read on this patent because AV1 codes its coefficients differently.
I didn't say it covered slotting it in to anything. I don't read your comment as showing how it is slotted in one "way" in particular, but rather how it is slotted into one thing in particular.