You may be absolutely right about a warrantless search discussed in the “See also”. EFF’s opinion (the main link) is about something different, though somewhat related. The situation seems to be…

Police procured a search warrant for defendant’s cell phone but were unable to execute the warrant because the cell phone was passcode protected and defendant refused to provide the passcode. Accordingly, the State filed a motion to compel production of the cell phone’s passcode.

EFF argues that even in this situation with a warrant, Fifth Amendment protections against self-incrimination means that the defendant can’t be forced to reveal the passcode:

“When the government demands someone turn over or enter their passcode, it is forcing that person to disclose the contents of their mind and provide a link in a chain of possibly incriminating evidence,” said EFF Surveillance Litigation Director Andrew Crocker. “Whenever the government calls on someone to use memorized information to aid in their own prosecution—whether it be a cellphone passcode, a combination to a safe, or even their birthdate—the Fifth Amendment applies.”