Blizzard talking about it would simply create more buzz and more bans. People were clearly dubious about it, hence they had to ask Blizzard. If you have to ask Blizzard if something is an exploit, you should play it on the safe side and avoid it until there's word of it.
Often times things like this are kind of grey, and in that case I agree with you, announcements and communication are great. But there was no grey here. If you have to go to twitter to ask Blizzard if it's ok, it's likely an exploit. And if it isn't, you'll likely get a response fairly quickly, as it's good for Blizzard to let the community know when something that looks like it might be an exploit isn't. But spreading the word about an actual exploit they may not be ready to fix is a bad idea, as it creates more work for them and results in more bans.