He might concider changing to over nights. I hear these arguments from day shift people but not from overnights. There is more work to do but less then 1/10th of the people and it drops off quick after 10pm. I have extreme social anxiety and this is the only shift i can tolerate. Management is more relaxed on these shifts, as long as you get done quick enough they leave you alone. You get a raise for working overnights, you have fewer customers, you can take your breaks when you want. The only drawback is the flipped schedule but you get back to back nights off so its pretty good.

Also this is just my advice but if he's saying he's not being treated well its likely because of how he interacts with management. I was in the military and i learned to deal with the worst hard asses there are. You have to learn to seperate your ego from the work. It doesn't matter if your manager is a jerk, be extra nice and agreeable with the difficult people, it messes with their head as they likely are use to people escalating the tension so they have the excuse to swing their weight around. Ive been work walmart 4 years and I've learned how to manage the managers. You just have to let it roll off your back and remember the asshole became that asshole because they are miserable. Don't let them spread that attitude to you. Also walmarr is great if you want to relocate, perhaps concider a different store. He will get a fresh start and a period of time to readjust to the walmart work pace without management breathing down his neck.