CPP11 — OBV GIOP clarification needed

Summary: On page 15-15 of the 2.3a core chapters, I am having trouble
understanding the wording in the first two bullets. The definition
of what the different bit values mean is clear enough, but the
rationale for when they are used is not.

Specifically, I don"t understand the subtle difference between
"the actual parameter is the same type as the formal argument"
(first bullet) and "the actual value"s most derived type is the
same as the static type of the position currently being marshaled"
(second bullet). Are these different cases? If so, what is the
difference?

resolved see above