Yes, you can definitely reduce the rest periods. BUT, make you aren’t rushing the workout and that you’re fully-to-mostly recovered when you do your sets. I deliberately made the rest periods a bit longer than you might be used to because I wanted to counteract the urge to speed through the workout in an attempt to make it into cardio. So, if I recommend 60 or 90 seconds of rest between exercises you don’t necessarily need to wait that whole time, but I don’t want you flying through each exercise without resting at all. If you finish a set and are immediately ready for the next set, I’d say you might not have pushed yourself hard enough on the set.