Does anyone out their have a problem unlocking the Devourer and the Tangalore entries?

I have a problem in understanding why I have to unlock any information at all. Geralt has been studying and fighting these monsters for almost 100 years. Why he he just figuring this information out now?

Even worse, how does Geralt know how to destroy certain monsters, but the information does not show up on those monsters until after he has killed one (e.g. in White Orchard, Geralt knows that Buckthorn can be used as a lure and how to "summon" a noonwraith)?