Ah! When it comes to arguments, yes, I do agree that their supporting examples really ought to be true-to-life.
But I don't think that's quite what was going on here.
munificent was using a metaphor in service of his plea, his encouragement, his advice that you really ought to consider making regular efforts at what you care about. To me, that feels a lot less technical and a lot more human than an argument does.
The difference between metaphors and examples might be that the important part of a metaphor is how it functions in context, how it adds to the metaphrand[1], and the important part of an example is how it functions out of context.
To give an example of metaphor: many Native American tribes besides the Lemhi Shoshone have stories that claim Sacagawea as one of their own. The stories—themselves metaphors for tribal values—are, of course, wrong, but they serve an important instructional purpose, nonetheless, transmitting values and custom in a narrative that inspires. In that case, it seems less important that the children of these tribes are hearing something factually incorrect, and more important that they are inspired by and identify with the story.
To give an example of example: if you're making an argument in court, you have to reference examples of past rulings that support your position. The strength of your argument depends completely on the validity of your examples, as they occurred outside the current context.
If you think I'm full of hot air, you're right, but anyway here is a list of famous authors explaining how fiction is truer than the truth itself: https://www.brainpickings.org/2012/01/27/famous-authors-on-t...
Thanks for coming to my TEDxHN talk.
1) Julian Jaynes, in the beginning of "The Origins of Consciousness and the Breakdown of the Bicameral Mind", does a lovely segment on how we only learn via metaphor, and in which he develops the terms metaphier (commonly, the metaphor itself) and metaphrand (the thing being described by the metaphor).