I don't think the distinction is meaningless, though, as I said, I do agree that exportable keys are more vulnerable than non-exportable.
What I understand the iCloud scheme to guarantee is roughly:
1. The TEE will not export keys except encrypted to the previously-established sync keypair. (IOW, it will only export keys after first encrypting them with the public key of the iCloud-sync keypair.)
2. The iCloud sync keypair will not be divulged by the iCloud server-side HSM except upon presentation of the correct auth credentials (your iCloud password or recovery key).
I think this provides meaningful security beyond keys sitting in plaintext on (FDE-encrypted) disk, namely, that malware running on the device cannot itself simply export the keys from the TEE. It must instead join a new keychain to the iCloud trust circle, as described at https://support.apple.com/en-hk/guide/security/sec0a319b35f/..., and to do this, it must be able to authenticate to iCloud as the user.
That's certainly possible--malware running on the device could phish the user's iCloud password, for example. But it's no longer a zero-user-interaction access to the synced key.
Again, clearly weaker than non-exportable keys, but still stronger than keys sitting in plaintext on disk.