I believe they call it a PROPHETIC illustration or PROPHETIC parable. Smart choice becaue the parables were used by Jesus to make a point, to warn or inform his audience, to clarify things they did not know, or were about things soon to come.
The parable of the FDS is a sort of a warning that Jesus will pass judgment those who as a a steward (or slave). The judgment can be a positive one but also a negative.
The parable of the vigins or the talents address more or less the same warning or lesson.
But these parables are not equal to a prophecy. A prophecy is about a specific future event, very clearly identified by all when fulfilled (i.e. even His opponents acknowledge Jesus existed).
But the WTS knows how to use words to their advantage and power. This is an excellent example of that.