Yeah, this is the same reason Apple avoids announcing products before they're ready to be sold, because they are so bad that if people knew about them ahead of time, they would never buy them.
Or wait, maybe it's that they want to generate interest in the app when it's actually available to buy.
That's a pretty decent parallel.
Another one could be to recent design changes by facebook, google reader, etc. No matter how good it is (and i'm not going to pass judgement on facebook design changes to avoid flamewars), it will almost certainly be different. Some people will like it, others won't, and the people who won't will be louder on the internet.
Now I think that DougZ has done an amazing job on isotropic. It's not "pretty", but it suits this communities (hard core dominion players) needs very well. It has a leaderboard, log exports for parsing, runs well on everything than touch devices where card re-ordering doesn't work. (Unless he's changed that?). It's fast, and because we all have 100% of the cards memorized, provides everything we need to play.
Even if everything else was the same, the commercial app will almost certainly cost money. That difference alone will cause some people to complain (isotropic had all of the same stuff and was free, why should I pay money for this?!?!?!) It will probably use the official card art. Some of us (myself included) will probably not recognize the cards (I haven't opened my physical copies of cornucopia or hinterlands), and might gripe about that.
So, I think I can understand keeping it under wraps.
That said, I suspect that the radio silence is more akin to review embargos of games or movies prior to their release date, and that we're going to dissappointed.
I feel like as a developer of a replacement system, I'd want to engage the hardcore-extremely vocal community to ensure that I don't fracture my fanbase. See
http://www.nowgamer.com/features/1065904/counterstrike_global_offensive_valve_interview.html for an interesting interview regarding the counterstrike beta, which attempts to address the concerns of both groups of CS players (those that prefer old skool 1.6 vs. CS:Source)
Maybe Jay already has, and
REDACTED just keeping his mouth shut.