The Javadocs currently have:
"true means the shape centered within the Region's width and height, false means the shape is positioned at its source position"

missing "is" between shape & centered:
"...the shape is centered..."

It's the same in the Javadoc for setCenterShape, isCenterShape, and centerShapeProperty.
https://openjfx.io/javadoc/19/javafx.graphics/javafx/scene/layout/Region.html#centerShapeProperty()