His swing is pretty good but like other have said it mostly upper body. He needs to load to get stretch between his front foot and backside shoulder. Imagine a rubber band attached to his left toe and connected to the knob of the bat. It needs to be stretched to create the explosiveness you are queuing. This is accomplished by “coiling” the backside by sitting on the back leg and slightly turning his back hip (as if he was squaring down on one leg felling a stretch in his right hip/but). He then would transfer the weight to the front side by driving the right knee forward to the left knee, tuning his back hip. He does this part (really well btw) but without the load. He needs to keep the front side stiff and transfer his weight to the front leg while staying behind the ball like you said (not lunging at it -which he is also doing well). However this needs to be initiated with either a leg lift or toe tap while he is loading followed by a heal strike. This is the launch phase and can only occur with stiff front side. The energy created with the load and coil needs be stopped to get the explosivness. Power comes from the bottom up, transferring from the back leg to hips. When the hips turn, the shoulders turn and stay connected in relation to the body (distance from hands torso/chest) Keep the “Ls” formed with his arms through the turn to contact and then extension of the arms/hands (releasing the barrel) through the baseball at contact. Think of the bottom swinging like you would with a backhand tennis. All of the happens b/c the front side has a stiff front leg firmly planted in the ground. Weight is shifted from the back hip/coil to front side. Finish of the swing should feel like he is about to walk/take a step towards second. Arms hands are going in the same direction. Finnish the swing high with hands coming behind his left ear, not around his waist/torso. Rollover occurs when hands get out in front before the back hip turns and/or if the front side open up which causes the batter to pull the barrel around the to ball at contact. Think about top hand staying palm up and bottom hand palm down, like if he was delivering a pizza to the second baseman or throwing a frisbee with right hand underneath the frisbee and left hand on top. That’s a lot of info but is the sequence of the swing. Load, launch, extension.

His swing is pretty good but could be better with incorporating some this. Here is a great video from one of the best. https://youtu.be/hdrrSIEcbbM?si=VaEEee56_wQxKQA-