I'm sorry, I'm not sure how I missed this post.
To answer your question, yes, that no contact info rule still applies to information that shows up on preview pages. I think it's just a matter of respect to the requesters that make their contact info available.
The internet is full of bots that crawl websites looking for contact info to use for spamming/nefarious purposes. I see bots crawling our forum threads all day, every day. Any one of those could be up to no good. Because all of our work threads are public, it's pretty easy find anything that gets posted in them. That's different for stuff that appears in a preview page on mturk. Most HITs require you to be logged in to even preview them, making that info harder to get at for non-turkers.
Another thing that tends to happen, is people will often attempt to post private info such as phone numbers, social media profiles, home addresses, etc while they're in the middle of a witch hunt over some stupid rejection that ends up getting overturned anyway. This often leads to excessive harassment and I believe some have even reported receiving death threats. The unfortunate reality is that there are a lot of shitty people on the internet, including mturk. Not everyone shows the same respect to requesters that a level headed person might. We feel it's best to try to avoid that by just not allowing any of that info to be posted publicly.
None of this means that you can't offer that info to others, though, or ask someone else for it. We just prefer that it be exchanged privately, rather than posted openly in the threads.