Sweet potato and Dioscorea are clearly horticultural crops because they are root/tuber vegetables used in human food and fit into the vegetable category of horticulture.
Peanut is primarily an agronomic crop but can also be included in horticultural crops in some contexts (home gardens, mixed cropping systems, etc.) due to its food, soil-enriching, and dietary importance.
Yes, Dioscorea (yam), peanut and sweet potato are considered horticultural crops, specifically under the category of tuber and root crops. They are grown for their edible underground parts and are important for both nutrition and food security.