Most iCloud data is end-to-end encrypted; Apple doesn't have direct access to your data. In the end they do own the OS and could potentially backdoor your device, but if you're worried about that... well, Lockdown Mode is moot at that point.
Apple refused an FBI order to decrypt a phone; however they allow the FBI to access iCloud data all the time. And iMessage is not end-to-end encrypted in iCloud at the explicit request of the FBI. https://www.reuters.com/article/us-apple-fbi-icloud-exclusiv...
Which makes it all the more ridiculous that sensitive things like messages, photos, contacts, and notes aren't, even as an option. Clearly the technical ability is there.
Worth noting Apple previously refused an FBI order to do just that. https://en.wikipedia.org/wiki/FBI–Apple_encryption_dispute