What provides “home run power” – is it the bat, or the batter’s swing? Both, of course.
Vanhoozer likens Scripture, the written Word of God, as the bat, and the triune God speaking through it as the batter. So the statements “Scripture is true” and “the living God speaks truly through Scripture” are not necessarily equivalent statements. The first focuses on the bat, whereas the second focuses on the batter.
…I personally think it’s better to simply say that Scripture is true and to let truth be the guiding understanding of Scripture. Especially since “inerrant” isn’t a biblical word. We can be fully biblical in describing Scripture with terms that Scripture itself uses, like “God-breathed” or “living and active” or “cannot be broken” and the like. But “inerrant” seems to claim something about Scripture that Scripture does not necessarily claim about itself, especially in how folks tend to use it or perceive the term today.
…Yes, Scripture is “inerrant,” if you still want to use the term – but it’s so much more. It’s a gracious, truthful, sanctifying Word of the triune Father, Son and Spirit.