It makes more sense if the direction is split from the unit in the sentence.
Consider: "after investigating response times and doing and doing a bunch of work, my PR causes a 30% reduction" - if you're busy doing lots of things and already have a lot of cognitive load, this could sound bad because the important phrase "30% reduction" is in there. You are a detail oriented person who is immune to this effect, but there are people who need help reducing their cognitive load in this type of thing.
You can help people reduce cognitive load by replacing "reduction" with "improvement" so they immediately understand that it moved in the right direction.
Consider: "after investigating response times and doing and doing a bunch of work, my PR causes a 30% reduction" - if you're busy doing lots of things and already have a lot of cognitive load, this could sound bad because the important phrase "30% reduction" is in there. You are a detail oriented person who is immune to this effect, but there are people who need help reducing their cognitive load in this type of thing.
You can help people reduce cognitive load by replacing "reduction" with "improvement" so they immediately understand that it moved in the right direction.