Pathfinder Discovery Mutagen not granting Mutagen class feature

Building a Character with Pathfinder Rules

Class: Alchemist (has Class Feature: Mutagen, temp bonus can be chosen OK)
then add
Archetype: Crypt Breaker (removes Class Feature: Mutagen, temp bonus cannbot be chosen OK)

adding the Discovery: Mutagen (Class Feature) adds the Mutagen as a Class Feature again but the Temp bonus cannot be applied in the Temporary Bonus section.