You may have been looking at an earlier (private?) draft revision of the guidebook that had those sections omitted. The draft book that is linked shows RL disc

You may have been looking at an earlier (private?) draft revision of the guidebook that had those sections omitted. The draft book that is linked shows RL discussed in Sections 2.6 (pp. 75-79) and 3.3.2 (pp. 122-125), while Neural Networks are briefly covered in Section 2.5.1 (pp. 62-74) with a note about DeepMind's DQN RL agent on p. 91.