They are looking to lower the percent positive number. There are obviously a higher percentage of positives among symptomatic people than non symptomatic so it can only help.
I don't think this is clear cut at all. When there's a rampant outbreak of a disease which can have very mild symptoms and pre-symptomatic positives, I think this is a huge gamble and may lead to a even bigger spike.
To be fair, to achieve what they want in the timeline that they wish (lower positivity rate within the next week), they don't really have another choice.