The prosecutor did not bring charges, so yes he did say that Cosby was ‘not guilty’. End of Story.
What the prosecutor did say was...
Castor said. “What I said was there was insufficient, admissible, and reliable evidence upon which to base a conviction beyond a reasonable doubt.
...
“As much as I wanted to go forward, there wasn’t enough evidence and prosecutors are bound by the law,”
...
Castor also said the alleged victim’s delay in speaking out hurt the case.
“You lose the ability to test for blood or intoxicating agents, whether she was drugged,” he said.
The prosecutor admitted to being tempted to bring the charges FOR THE NOTORIETY IT WOULD GIVE THE PROSECUTOR.