Unlike other Advanced Hizite books, when you mouse over the Advanced Hizite Armorer's Volume I, II, or III, the recipes contained within don't pop up. If you choose to Examine the item, the recipes are listed. It's just the mouseover preview that's faulty.
This is common in books that have more recipes. I'm not sure exactly where the cutoff is, but most books with lots of recipes don't show them on the preview while those with only a few do.
Look again. No lies detected. One is weaponsmith and the other is armorer. And yes, it is based on the number of recipes in the book. If there are few enough recipes, it displays them, otherwise, it just displays the number contained.