This is not a finger-pointing exercise. This is just odd-ball stuff where there are either minor problems or discrepancies in the documentation and you can't trust what the game (or documentation) is telling you.
And speaking of documentation, take the Prima Guide with a grain of salt. This is not to bad-mouth Prima or the author, both of whom undoubtedly went to great pains to insure the accuracy of their information prior to sending the book to the printer. However, there is a time-lag between the time that a book goes to press and a game "goes gold," during which there are additions, deletions and tweaks to the game which cannot be included in the final version of the book. For the most part, the Prima Guide is very well done and as accurate as can be expected under those circumstances and it will generally keep you pointed in the right direction. Throughout my pages I've tried to point out where the Guide's information is outdated. This is neither a good thing nor a bad thing, it simply is.
1. You'll see loading screens that tell you that Novices in Sneak gain no damage bonuses for successful sneak attacks. Not so. Novices gain a 4x damage bonus when attacking with a melee weapon and a 2x damage bonus when attacking with a bow. The bonus increases to 6x and 3x, respectively, at Apprentice level.
2. During the "Uncovering Your Roots" quest (a miscellaneous quest that you pick up the first time that you pick Nirnroot), you'll eventually get a pop-up journal entry that tells you that you have found 10 Nirnroots and should take them to Sinderion. This is a literally true statement. You have, indeed, found 10 Nirnroot plants, but that does not necessarily mean that you have 10 in your inventory. I managed to lose a couple somewhere along the way (probably munched 'em by accident) and got a message saying that I had 10 when I knew that I only had 8. Check to see how many you have before you go talk to Sinderion. He's not going to want to talk to you unless you have 10 plants in your inventory. PC players can probably find a mod that will fix these little boo-boos, but XBox players just need to be careful.
3. The game manual lists the Block skill as being governed by your Agility attribute; it is actually Endurance.