Not sure where you looked, however here is something from a Guest services page for Epcot.
Credit Cards
Visa is the proud sponsor of the Walt Disney World Resort. Traveler's checks, cash, JCB, Diners Club Card®, Discover®, MasterCard®, American Express® and The Disney Credit Card are also accepted.
WDW started accepting Discover card about 4 years ago. There was not much fanfare with the acceptance since Amex was still an offical sponsor. I hope this helps.