Can someone please clarify why Question #6 is not flipped and negated? I do not understand the explanation of "requires" and "is required for"

So, in this lesson we're learning how to negate a relationship, but previously we were negating conditions/logic? I'm a bit confused on how to put into words the difference between

A->B

/B->/A

and this new process that goes:

A->B

AB

If the indicator word is "all", how do you know whether to take the negation of the sufficient condition or this new negation process for "some"? Or does it boil down to what the question stem asks? Thanks in advance for any help, I'm a bit too confused to explain what exactly is confusing me...