This explains the mediaplay...
The charges were from 2016-2017 and the accusations came out were almost a year ago. It was impossible to prove the acid issue since all the evidence left was He Said She Said. Say he hadnt done anything a month or two before Dispatch exposed him, he still had a fair amount of time for the drugs to leave his system before they tested him.
Yoochun was caught, tested and exposed within a few months while prosecution dragged their feet hard with this.