It means a bias of coming together toward a tester's preferences. Do people excel on the few narrow performance meausures you find most correlated with intelligence?

There are divergent aptitude tests measure quantity and diversity of answers to a given question opposed to the one desired answer. Divergent tests are rarely performed, but at a stronger measure of creativity and problem solving which is typically what people actually want when they say intelligence. The reason why convergent testing is preferred over divergent test is because it is easier to measure and those simplified measures are easier to compare.