Perhaps they were quietly working on changes all during the playtest (based on customer input), but said nothing publicly out of fear of you.
Moi? Why, I have no idea what you're talking about
In all seriousness, while it's certainly possible that there was a set of "backup" mechanics being quietly tested, I can't see any reason not to release them to the public playtesters, unless they suddenly went cold on the whole notion of public playtesting.
That's a distinct possibility, I suppose.
Myself, I'm no fan of the
public, unstructured "here's the playtest rules, have at 'em" approach. Between those who (a) unconditionally love the system and attack anyone who says otherwise; (b) unconditionally hate the system and attack anyone who says otherwise; and (c) change the playtest rules without disclosing this in their feedback; I'm not real sure that there's that much playtesting benefit to be gained.
That said, a purportedly "public" playtest might produce positive marketing spin (if the game is actually any good), so it might well be a good marketing tool. Of course, if the resulting spin indicates that the game is likely to be badly flawed, then I could certainly understand a company losing enthusiasm for public playtests. But a company that uses public playtesting primarily for marketing gets what it deserves, IMHO.
If I were gonna use a playtest to generate good buzz, I'd (a) be sure that the mechanics are fundamentally sound, statistically; and (b) that the mechanics actually work reasonably. Mongoose failed to do this, IMHO, and I don't think that the playtest generated a net benefit for them.
I'd probably also release the subsystems separately and ask for comments on just those systems. So, I might release the character generation system first and ask playtesters to simply create bunches of characters and run through various skill tasks. Then, a month later, after the character generation system has been worked through and pretty much defined, release a combat system, with the same request -- run through combats and report back.
By isolating the playtesting to discrete systems, I think you'd get the highest quality feedback, since the playtesters are forced to focus on a particular thing. (In the interest of time, I don't see any harm in simultaneously releasing systems that are unrelated -- character generation and world creation for instance).
And if you *do* release a public playtest document, the designer should provide regular feedback in the forum. *Especially* to critics of the system. This does two things -- first, it lets the player know his critiques are being considered and that the designer is trying, in good faith, to build a good game. Second, it prevents fanboys from prematurely leaping to the game's defense and creating a flamewar. (This also keeps the fanboys from being humiliated when the designer abandons the system that they vociferously defended).
The absolute *worst* thing a designer can do IMHO is to release the playtest rules publicly, refuse to respond to legitimate criticism, then arbitrarily lock threads that have gotten heated largely because the designers have not responded to criticisms and allowed fanboys to defend the system. I also would be scrupulously fair in warning both fans and critics about unacceptible behavior. If anything, I'd probably give more rope to the critics because (a) they'll be outnumbered in a normal forum and (b) the purpose of the exercise should be to uncover flaws and correct them. Critics are, uh, critical to that.
BTW, I walk the walk, as anyone who visits the Fistful of TOWs email group can attest. I have *never* banned anyone for being offensive and we have had some epic debates (the "Great Russian Tank War" comes to mind). While it's a small forum, there are over 500 members and a couple of dozen very opinionated gamers. As a game designer, I love those guys, even if I sometimes think that they're crazy. Their nitpicking, grousing and fussing has done nothing but improve my game.
In my opinion, Mongoose's management of their forum indirectly created most of the purported incivility that arose in the MGT forum. I sincerely hope that they learn from this experience.