It's unrelated to the physical connection, but the drive encryption used on the built-in drive keeps its keys in the CPU's secure enclave, so dead CPU == data lost, regardless of whether the ssd itself is damaged.
Obviously if you used the same encryption scheme on a removable drive you'd hit the same issue - but most people don't do that, because storing the encryption keys in the Secure Enclave makes your drive effectively no longer removable.
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It's unrelated to the physical connection, but the drive encryption used on the built-in drive keeps its keys in the CPU's secure enclave, so dead CPU == data lost, regardless of whether the ssd itself is damaged.
Obviously if you used the same encryption scheme on a removable drive you'd hit the same issue - but most people don't do that, because storing the encryption keys in the Secure Enclave makes your drive effectively no longer removable.