My understanding, which may be incorrect, is that while one of the base optimizations he performed requires the second 4MB, most of the rest of the optimization

My understanding, which may be incorrect, is that while one of the base optimizations he performed requires the second 4MB, most of the rest of the optimizations definitely do not. So while I would not be surprised if he made some changes that assume more RAM is available in total beyond what was mentioned in the video, I believe most of the refinements covered could still be applied without.