From the photo 1, it is yes. That short wall is a bearing wall because the rafters sit on them. Think of it as a regular wall which is reinforced by usual ceiling joists or collar ties. Maybe a nitpicking but I wouldve put the braces on the 2x4 plates than on the rafter ends. As they are, the reinforcement depends on the nail connection between the rafters and the plates.
Im not sure and you may want to see an engineer but you could replace the braces with metal angle or i beam for the space though not worth the cost for the storage.
After the fact, but the rafter bays in photo 2 should have vent space.