Backyard chicken owner here! Yup, very firm yolks. However the color can fade in the winter when they don't get many greens or sunlight. Evidently you can add turmeric to their feed to enhance the color, but I've never cared to try.
There's an interesting later passage about exactly that:
"Joel told me that when he first began selling eggs to chefs, he found himself apologizing for their pallid hue in winter; the yolks would lose their rich orange color when the chickens came in off the pasture in November. Then he met a chef who told him not to worry about it. The chef explained that in cooking school in Switzerland he’d been taught recipes that specifically called for April eggs, August eggs, and December eggs. Some seasons produce better yolks, others better whites, and chefs would adjust their menus accordingly."
