work set - something that is going to make me work.
I would consider that a work set in this scenario. If this person had 2 warm up sets, he's still really 'warming up' with this set. You need to get your body accustomed to heavy weight before jumping to the big stuff.
At the same time, not sure why they went from 400 to 225x10. If you are going to lift heavy, then lift heavy. If you are going to lift for reps, then lift for reps.. not getting stronger by mixing it, not getting endurance by mixing it. I would have went to 425x2x1.