I was recently converted to a Signature VISA card by Bank of America and the credit card invoice lists a credit limit on it, so it is not a blanket permission to charge to the millions of dollars. My recent credit report also listed the credit line amount for this card. I don't have any cards that list "no credit line" on my credit report whether it is a Signarure card or not.
I'm not surprised that Citibank hasn't updated the website about the obsolete/new account options. Since it isn't effective until July 2010, they may drag their feet and not change until that date is near. Just like how my company still uses Internet Explorer 6 before the last minute when Microsoft decides to stop any further support for it and then make a massive network upgrade.