Yes it is an illustration. Yet, none of us doubt the application of scripture that refers to a wicked slave class; logically then there would be a counter-application of the faithful class.
Jesus frequently asked and answered his own questions.
"How then, should we pray? You should pray this way..."
"Which one among you is without sin? Let him cast the first stone."
"Who really is the faithful and discreet slave whom the master has appointed...?"
No, the application here is very real. In the illustration, though, it wasn't until the master returned that the identity of the FDS was revealed. "But," someone might say, "Wouldn't you be able to identify the wicked slave class by their actions? and the FDS by their actions?" You'd think so, huh? But the FDS didn't get recognized or rewarded until the return of the Master.
The question here, is has a group of almost exclusively white, elderly white men, set themselves up as the leaders of the FDS? And, is a GB necessary when there is an entire class of 144,000 who speak on Jesus behalf?
Have you ever read some of those life experiences of the annointed? They feel an almost wierd call to devote their ENTIRE lives to preaching the Gospel. I can tell ya, that ain't me. There are people of every walk of life, every culture, who feel drawn to Jehovah and Jesus in a special way. Whether 9 of them should be a 'Governing Body' remains to be seen.
Even Jesus said there would be those who performed MANY powerful works IN HIS NAME, and yet then he would confess to them, "Get away from me you workers of lawlessness. I never knew you."