The Interactive Split Tool doesn't show you a block, it shows you an orange line where the split is going to occur. The block you refer to may just be a highlight in the book to show you what they are referring to or the author has Select by Faces turned on and is hovering his mouse over the face, at which point it should turn orange.
Dave Baer
Professor of Digital Arts
Digital Media Arts College
Boca Raton, Florida
dbaer@dmac.edu