Why is 称 used instead of 显示 in 消息称，苹果已经开始……?
显示 = indicate

消息显示 - The announcer observes the information that's available and provides a report to the audience
The source of the information may or may not have provided the material directly to the announcer

称 = announce/ claim

消息称 - The announcer directly relays the announcement or claim from the source of information to the audience
The source of the information has made the announcement/ claim itself
Also:
证据显示 - evidence indicates (evidence doesn't make claim)
发言人称 - the speaker claims (speaker announces, not indicates an announcement)