That's because Tico was designed decades ago, at the time destroyers were much smaller vessels.
Zumwalt is help setting a new standard for new generation destroyers - if that is a DDG, 055 should be, too. The media is either still using old school standard they were used to, or purposely using the cruiser term to exaggerate PLAN threat and advancement.
Unfortunately, surface combatants these days are not mutually exclusive in modern and traditional class designations, whether we use capability or displacement as measures.
Besides, just because the USN calls DDG1000 a destroyer doesn't mean it makes sense for other nations to do so. JMSDF calls their hyuga class "helicopter destroyers". Hell, prior to 1975 the USN, they considered some of their nuclear cruisers as frigates!
Ultimately, what we call a class depends on what everyone else is calling their own ships, along with more "traditional" descriptors, but also common sense. Considering all that, I do not think there is any reason why 055 (or indeed, Zumwalt) cannot be called cruisers, as much as Ticonderoga or Sejong (or even Burkes, Atago, Kongo).
Zumwalt might be a groundbreaking design, but it's a little early to judge whether it is setting any kind of standard. If anything, its aims now seem over ambitious if not a little vague, and certainly it is too early to think it will have the kind of influence to redefine an entire class of warship like HMS Dreadnought. At any rate, it isn't enough to disallow the weight class of what we perceive as cruisers as below 15,000 tons.
And, just for the record, in what few instances we have of the PLAN referencing 055, they call it a "large destroyer".
(I'm adding one more, of course)