A question about: Braised Pork Roast with Onion Jus, Pears, Turnips and Potatoes

I have a question about step 5 on the Braised Pork w/root veggies from Tom Hirschfeld. It says:

"...slice the pear, turnip and potatoes lengthwise to get two 1/2 inch pieces from each vegetable and the fruit. You may only need two veggies or fruit each to do this the third is just backup."

Should that be 2-1/2 in pieces? If you only need two half-inch pieces from each item, how would you need a back-up?

Thanks!