High reps are great, but that sort of weight, Wills could do it all day. It's going to give him a pump sure, and it's better than nothing, but if your body is used to 250kg for 10 reps, it's probably not going to grow all that much when you do the same reps at 120kg
I'm a big believer in heavy weights not being the most important thing when aiming for size, but you still have to at least stick to what your body is used too. Going backwards in weight, no matter the form or reps will not get you anywhere