https://www.apple.com/business/docs/iOS_Security_Guide.pdf

The short version is that your passcode (whether four digits, six digits, or a full password) is combined with an encryption key embedded in the device in a way that's supposed to be impossible to extract, and used to derive the encryption key used to protect your data.

The device you linked to relies on a vulnerability in the US, where it would report that a passcode entry failed before recording that failure to nonvolatile storage. Normally, the device starts adding more and more delays to passcode entry after a few failures. By cutting power to the device immediately after it reported failure, it bypasses those escalating delays. As your link mentions, Apple fixed this vulnerability in a subsequent OS update, so that hardware only works on older OSes. This phone's OS is too new.