By definition here, in the Webel recipe for pragmatic SE with SysML, the custom Stereotype keywords «blackbox» and «whitebox» refer specifically only to the 'problem' zone and NEVER to the 'solution' zone (as opposed to more general natural language uses of the terms white-box and black-box).
The natural language term 'black-box' can refer also, of course, to a design (implementation) element seen from the outside, and 'white-box' to a design (implementation) element seen from the inside with its gory details showing. They are NOT the sense in which the Stereotype keywords «blackbox» and «whitebox» are used in the Webel recipe for pragmatic SE with SysML.
In the Webel recipe, both «blackbox» and «whitebox» are by definition here special cases of «logical».
BTW: This Webel terminology aligns well with some formal SE methodologies, but not with all. Each formal SE methodology defines the meaning of the terms as used within them. Those definitions (however correct for their intended use with those standards) are NOT relevant here; if you are using one of those formal SE methodologies or standards, by all means use the terms as defined in them (for which there may be existing stereotypes in a provide Profile).