Indeed, on this figure, the first face 012 points inwards using right hand rule.
However, we can read the opposite in the VTK doxygen generated documentation :
The wedge is defined by the six points (0-5) where (0,1,2) is the base of the wedge which, using the right hand rule, forms a triangle whose normal points outward (away from the triangular face (3,4,5))
Last point, this figure in the VTK documentation shows the opposite as well (same as VTK doxygen generated documentation).
I am pretty sure it is a figure error in the VTK documentation but as the VTK readme “Reporting Bugs” paragraph states, one must first “join the VTK Discourse forum and ask about the expected and observed behaviors to determine if it is really a bug” before to “open an entry in the VTK Issue Tracker”.