[Cyclop]

There are sooooo many details in the Player's Handbook alone, that it is hard for any group or DM to ensure each player knows them before or exactly when they are needed.
I do see a difference in opinions on the Monster Manual knoweledge as I always viewed that information as something most of the character's in the game we are playing should have some knowledge of their environment and foes. Especially a hostile one. IMO that's like someone living in Alaska, uncertain what local wildlife could be dangerous and then not knowing what a threat an African Lion could be. IMO just reading the Monster Manual for a new person helps understand the game more. Just reading what the beast can or can't do doesn't in any way imply how the DM will use them in a setting.