The scenario is not evidence at all, fictional or not. The reasoning involved might count as evidence depending on your definition, but giving a concrete example is not additional evidence, it only makes things easier to understand. Calling this fictional evidence is like saying that an example mentioning parties A, B, and C is “fictional evidence” on the grounds that A, B, and C don’t really exist.
The scenario is not evidence at all, fictional or not. The reasoning involved might count as evidence depending on your definition, but giving a concrete example is not additional evidence, it only makes things easier to understand. Calling this fictional evidence is like saying that an example mentioning parties A, B, and C is “fictional evidence” on the grounds that A, B, and C don’t really exist.