I think working at slow speeds has huge benefit’s but I actually think changing speed is a huge skill set. learning to move at different speeds can be a good way to up skill.
Although Tommy is doing this for a technical change or calibration (I believe) which is so good for understanding movement. I personally like to make changes at slower speeds as I feel my brain takes the information a little better.
But I think this takes skill and discipline for sure to do what Tommy is doing here.
Original Video credit : @englishlouis1