roAssociativeArray.append() with duplicate keys [solved]

I notice that documentation has been updated to say

"ifAssociativeArray.Append(aa as Object)" wrote:
... If any key in aa are already associated with a value in this AssociativeArray, the current value is discarded and is replaced with the value in aa.

So it is behavior (B), the new AA overrides old AA content in case of overlapping keys. As any experienced developer would expect but now is in the RTFM and can be relied upon.

My gratitude goes to the forum's patron saint, RokuMarkn - thank you!