That's not terribly surprising. They want to keep expectations in check. And almost any site runs a risk of problems if everyone shows up on an arbitrarily arrived at day. But it also points up one of the underappreciated problems the White House has had - a mix of policy, messaging and technology.
The administration actually has a lot more levers to pull to drive people to the site and to sign up. But there's really no point in pulling those levers (quite the opposite actually) as long as the website is sub-optimal or not working at all. Not only are you driving people to a bad and frustrating experience. But as long as the website is hobbling along, adding more people just makes it hobble more.
That's all commonsense. But it also explains why the White House has been slower on the messaging uptake than a lot of the laws supporters have liked. It's hard to be out there hammering the point of how much money you're going to save on the exchange if people can't go there yet and see if it's true or if you have to say well, the exchange plans kick ass and you're going to love them. But just don't go check them out quite yet because the site's broken.
There's been a similar pattern on the private insurance side. There was supposed to be a ton of insurance carrier advertising in October and November aimed at selling exchange-based plans. But that was scuttled as soon as it was clear that the site wasn't working. Notably, it seems like that money will start flooding back in as soon as the website is functioning.
Obviously, this isn't the only reason for the slack messaging out of the White House. The main issue is that messaging really tough when your product isn't working. And the White House made that bed for itself. But it's another example of pervasive the effects of the failure of the website - for at least the first six to seven weeks - really were.