My thought was that the T2 chip is responsible for rate-limiting access to the Secure Enclave. Specifically, for rate-limiting attempts to derive a key from as user-supplied password and the secret in the Secure Enclave.

This allows for weaker passwords to be used, because brute-forcing requires the secure-enclave in the loop, and access to that enclave is rate-limited. Drop that rate-limiting, and the brute-force attack becomes a lot more viable.

As far as I know, this was at stake when the FBI wanted apple's help a while ago to decrypt an Iphone. However, I have no idea whether this is the same scheme used for MacOS devices. Nor do I know whether the T2 chip is actually responsible for rate-limiting.