A “specification” which is based on just “the desired behavior in a few specific examples” seems to allow undesired behavior without it being clear whether said behavior is allowed by the spec.
That to me doesn’t seem like what a “specification” is.
Now, maybe having good examples is more important for business use cases than having a specification.
Where X, Y and Z are very specific.
These example scenarios work well as a communication medium for discussing intended program behavior as well as translating well into tests.
>enumerate every possible combination
Whereas if you start doing this you will probably confuse your stakeholders.
Specific examples tend to make better specifications.