The sub-unit rumors weren't necessarily proven to be false...it could have been that CCM just wasn't ready for the news to be announced yet, and obviously the mention of Double Sidekick being the primary producer was incorrect. The girls are sticking with Shinsadong Tiger for their producer for the track.
And yes, Hwayoung was expelled from the group, but of course they aren't going to put that in their official announcement for this sub-unit. Which sounds better, being expelled or withdrawing from the group? Haha.
Like someone else in this thread said, "Rural Life" sounds like it could be a very rough translation at this point, so who knows? Or maybe it has to do with their concept. Either way, it sounds intriguing, and with Shinsadong Tiger behind it you know it's going to be a catchy, glittery dance-pop song.
As far as the press release stating that it will "mend people's hearts," it's more or less saying that this is CCM's way of slowly reintroducing the group back into the public eye. At one point, EunJiMin were the group's three most popular members, so of course CCM wants to remind people of why they were considered the holy trinity in the first place, and Areum is the new kid in town, so she's in the unit to get more exposure as well.
Ultimately, it's like some people were saying...I don't think T-ara really has anything to lose in Korea at this point. People are going to hate regardless of what they do, but people will also still buy their music and support them if their output is good. Just look at Sexy Love, it may have not done as well as their past releases, but they put out arguably one of the best songs of their careers and killed their performances, and the song did pretty damn good. I think this sub-unit is a good way of testing the waters, so to speak, and I'm sure that it doesn't hurt that sub-units are the big thing in K-Pop right now, like you said; if this goes well, we'll get a song from the full group in a month or two, and if it fails, we'll have a bit longer to wait than we thought. I'm inclined to believe that it will do well though.