Another example is WhatsApp on Android, by default when backups are enabled, they are stored unencrypted in Google Drive. A good counter-example is Signal, which opts out of backups on iOS and Android and the only option is to do E2E backups to their own servers.
I'm also fairly confidant in Apple's full disk encryption, they've gone to court to defend it.
FWIW, in the last leaked report, iPhone was not an issue AFU for Cellebrite (macOS is most likely even easier due to looser security):
https://discuss.grapheneos.org/d/14344-cellebrite-premium-ju...