i’m not sure but they may be speaking about rinzai zen. watched a few bits and bobs about rinzai and some of the practices are kinda of that “willpower” ilk. dunno, never practiced it, not my vibe.

they definitely were not describing soto-zen tho, that’s for sure.

edit — i find it almost koan-esque that there’s two schools referred to as “zen”, both of which generally dislike the label “zen”, both of which have very different practices and methods.