They do that a few times a day, it's super cute. Oliver gets treats too, romaine lettuce and carrots, but it's off camera in the other corner of his stall. Some people were complaining that Oliver wasn't getting treats so now sometimes they'll give treats to him through the fence in April's stall so people can observe it happening.
Most evenings from 5pm to 6pm PST they will open up the live chat feature next to the video and the zookeepers will answer questions. (It's also opened up to donations) At the end of that session they'll give the treats to the giraffes and then eventually turn out the lights for the evening.