That means that simply following any runaway trim procedure will lose the precious seconds needed to discover that although you are pulling back on the column, the automatic nose down trim is still being activated.
Your statement completely ignores the fact that if a pilot is pulling back (is there any other way to pull) on the control column and they find that it is getting heavier, then they would naturally and instinctively use rear trim (nose up) using the electric trim switch on the column, which would then inhibit MCAS operation.