tldr; former Apple employee claims that Apple snooped on his privacy to collect evidence for a lawsuit, using screenshots from the supposedly end-to-end encrypted Messages messaging app from Apple. [1]

Is it possible for Apple to collect these screenshots, without having compromised the privacy guarantees of its Messages app?

From Apple's website: "End-to-end encryption protects your iMessage and FaceTime conversations across all your devices. With watchOS, iOS, and iPadOS, your messages are encrypted on your device so they can’t be accessed without your passcode. iMessage and FaceTime are designed so that there’s no way for Apple to read your messages when they’re in transit between devices." [2]

[1] https://www.bloomberg.com/news/articles/2019-12-10/ex-apple-executive-accused-of-betrayal-says-he-was-snooped-on

[2] https://www.apple.com/privacy/features/