not matched by vs. unmatched by

Solution 1:

Among the many meanings of match, two are relevant: one of equality and one of implied comparison.

a match =

a person or thing that is equal to another person or thing in strength, speed, or quality:

"We are matched in strength"

to be less powerful or effective than someone or something else:

"Gibson ran well but was no match for the young Italian."

Cambridge dictionary

Therefore, either of your statements may be understood simply to say that A and B are not equal, without making any comparison.

And either may be understood to imply that A and B are unequal. Which is the bigger may only be understood from context and not by the order in which A and B appear in the sentence. Consider:

"The beans in a jug are unmatched/not matched by the beans in a silo."

"The beans in a silo are unmatched/not matched by the beans in a jug."

The order of A and B is irrelevant; we understand from each statement that a silo holds much more than a jug.