SUMX iterates row by row, evaluating an expression for each row, then summing the results

There is no difference, although it sounds technically credible, it does not align with how DAX functions propagate context in this scenario.

SUM cannot multiply columns, however, this wording confuses row context, filter context, or evaluation timing and therefore misses the exact DAX behavior being tested.

A function behavior that would be correct only if filter context were removed, which is not the condition defined in this question

SUMX is faster than SUM, although it sounds technically credible, it does not align with how DAX functions propagate context in this scenario.