They're more than trying to imply it. Apple says "This is the tip of the iceberg", and a lawsuit is necessary to uncover the full scope of what they think OpenAI has to hide.

> As far as I am aware, employers aren't entitled to exit processes so long as they get their property back.

They're not, but one of the defendants allegedly dodged returning his company laptop. It's then alleged that he used it to continue accessing Apple documents after he'd already left, and coached at least one other person on how to copy confidential documents without alerting Apple's security team.

If these allegations are supported, it seems pretty reasonable to wonder whether there might be more people he coached and what documents they might have copied undetected.