I haven't tried it personally but multiple sources seem to confirm that this does indeed work.
There are a couple caveats to be aware of though. One is that this is NOT a permanent unlock, since not only do you need to be jailbroken, but you need to repeat the unlock for every new SIM card. You can be sure that Apple will try (and probably succeed) to close the vulnerability Sam uses, in future updates.
Secondly it's still obviously not as good as a carrier unlock.
However it's still a valiant effort at undoing some of the exploitation that the absolute absurd practice of phone locking in the twenty-first century results in.
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