This stretch is good for a warm - up because it does a great job of activating and recruiting lots of muscle groups as well as increasing your body temperature. (weckmethod.com)
Greater hormonal response: Doing an intense, high resistance, compound exercise that uses lots of muscle groups simultaneously will trigger a few different things in your body. (neatstrength.com)
It trains a lot of muscle groups at the same time, trains movement patterns that are heavily relied upon in rugby (hip and knee extension + a ton torso stability), and it can be heavily loaded, which lends itself to strength development. (rugbystrengthcoach.com)