can this also be used on a 3 step stringer?

The LSCZ is limited by its allowable loads (which can be found at the following link: https://www.strongtie.com/deckconnectors_decks/lsc_connect/p/lsc), not by the number of steps. I believe the "2-Step" reference on the Lowe's page is referring to the 2-step process of installing the part - attaching to the header, then attaching to the stringer. At the link provided above, you can see an installation video which shows the LSCZ used with a stringer having several steps. Thank you!