Well, I think the point is that while the wait times won't be shorter, the number of people in line might be shorter. With FP they often put 80% of the people through the FP queue, so if the old line had 2000 people in Standby waiting 60 minutes, the new line might have 600 people in standby waiting 90 minutes.
Pirates has the problem that the queue often overflows out into the park quite signifcantly - and this might alleviate that.