It's a different exploit. The original exploit is an issue with the Tegra's recovery mode (RCM), requiring a USB payload to be sent to the Switch at boot every time.

I believe the hardmod is a voltage glitching exploit, as described for the Vita here: https://yifan.lu/images/2019/01/Injecting_Software_Vulnerabi... . It is able to inject code through the onboard memory then load a payload from a memory card rather than USB.