A participle can describe the occurrence of a state or quality. In a circumstantial position an affirmative imperfect likewise often presents an attendant, non-permanent quality. This common descriptive force helps explain why the imperfect may behave like a single-word ḥāl with respect to the linking wāw.
But a participle and an imperfect are not semantically identical. One is a nominal description; the other is a verb bearing its own temporal and aspectual properties. The analogy concerns the relevant circumstantial function and should not erase their differences in grammar.