Sorry for the confusion regarding this, but this is indeed working as intended. Unfortunately, it looks like a slight translation error crept into the patch 1.18 notes about this, which we'll work to get corrected.

Skill points are granted for completing main scenario quests and sidequests. The reason that class quests don't offer SP is due to the fact that it was intended for classes that were offered the quest to earn the SP, but since the system currently is not set up that way, we decided not to have them grant SP. We're working to improve the system going forward.

*Edited my error as pointed out below.