Those datacentres would be in the same position of trust as a VPN provider in that the data must be unencrypted at points in the process.
They could be making it very safe, and the things apple says they are doing would make it as safe as possible, but as a user there is no way of verifying the claims.
Have you read the PCC whitepapers? Are you saying the user-facing verification methods in them are insufficient, or vulnerable, or just false?
> as a user there is no way of verifying the claims
I think this sums up what it's like to be an Apple user pretty well. With their heavy proprietary and closed approach, all users can do is "trust" them.