Not every type of building can generate in a village e.g the large plains library never spawns in plains villages but only the other library variation generates. I have been going to hundreds of different plains villages on many different seeds and have never found a large plains library or some of the other houses that generate. 

(I did end up finding a plains fisher cottage generate naturally but it is the only one I have ever found out of hundreds of different plains villages I have come across) 

seed for plains fisher cottage: -8147983463685324578 (it's at spawn)

 But this issue and MC-147989 are still relevant