Just a quick pass to check for holes
If they silently release it to experimental, within 5 minutes people will notice and start telling everyone in the world that a new version is out, and half of the people that hear about it will start playing it. When bugs get found there will suddenly be thousands of complaints about how terrible and bug-laden the new version is. When people playing the new terrible bug-laden version that was forced upon them wasn't advertised anywhere but on the forums there will be dueling complaints about how "they knew what a steaming turd this was so they tried to hide it on their forums" and "they only care about the shills that are active on their forums and don't give a damn about all their paying customers."
And when anybody tries to point out that experimental should be expected to have issues no one will listen.
There's plenty of people who understand that experimental is experimental, and who don't mind dealing with some bugs to get new fresh goodies, but the people who don't seem to understand are far far louder.