If you are successful at astroturfing and have good stats to prove it, what would be your motivation to hide that? Of course you would not want to reveal specific campaigns, usernames & subreddits you used, but what would be your motivation to hide the stats that are not identifiable? Your corporate identity would not be linkable to astroturfing usernames anyway - that's kinda the point of whole enterprise - so why not make it publicly available?
OTOH, if you know or suspect that astroturfing has a very low ROI, you have lots of motivation to not publish anything, but instead tell the clients: "our ROI is spectacular, but unfortunately we can't show any data or stats because you know, we have to do it in secret, so just trust us and pay us $TONS_OF_MONEY, and it'll all be awesome!"
OTOH, if you know or suspect that astroturfing has a very low ROI, you have lots of motivation to not publish anything, but instead tell the clients: "our ROI is spectacular, but unfortunately we can't show any data or stats because you know, we have to do it in secret, so just trust us and pay us $TONS_OF_MONEY, and it'll all be awesome!"