Well, silence is any magic users bane. The place the thu'um user has an advantage is that they're generally Nordic, and therefore still capable of smashing your face manually.
Manually, interesting terminology.
The first mortal to weave 2 enchantments simultaneously learned the technique from a dragon...
I'd put that book in the category of gameplay excuses. Along with the levitation act, Cyrodiil Once Jungled, and the manual of armor maintenance. Much easier. You have to be a mental contortionist to explain the difference in terms of lore, especially between games.