The idea is that the more pressure you use, the more unwanted materials like fines and oils will get though the paper. So if you press slowly and stop when you hear a hiss, you should have a better brew.

It does make sense, if imagine pressing through in 5 seconds vs 30 seconds, that the paper filtration would work better in the slower press. But I'm not sure if anyone has scientifically measured this.

Actually wait, it's coffee. Someone has definitely scientifically measured it and probably published a two hour YouTube video with their results.