Can you explain the difference a bit more, and why it's more than just splitting hairs? Is it because TPM is a specific standard for implementation of a secure co-processor, whereas Secure Enclave is part of a larger SoC (T2), which while it could be considered an implementation of a secure co-processor, is distinct from the TPM standard?
In researching this comment I learned that the T2 chip actually runs its own operating system (bridgeOS), so I can see why you'd call it an oversimplification (or muddying the waters) to equate it to a TPM.
The TPM is an TCG standard (also ISO/IEC 11889), and specifies commands that support a lot of use cases. The Secure Enclave from Apple is something simpler and more restrictive, that is tailored only for Apple's use cases.
AFAIK, and it's hard to find the info since I don't have it handy, so I don't want to devote the searching time, but bringing it back on-topic, all disk i/o has to go through the secure enclave for encryption and decryption. i believe this is better documented on mac than iphone. the data storage is always encrypted since T2. If filevault is enabled, then the user's password gets mixed in with the T2 hardware keys. Because those keys can never leave T2, all disk i/o necessarily goes through it.
In researching this comment I learned that the T2 chip actually runs its own operating system (bridgeOS), so I can see why you'd call it an oversimplification (or muddying the waters) to equate it to a TPM.