I've had horsehair gloves, loads of every kind of boxing gloves and with horsehair fight gloves you can wear them in a little on the pads before the bout and keep pushing down into them, such that the padding moulds around your knuckles moreso than with other types (like, you can feel your knuckles pushing through into the lining of the leather almost, especially once you wear them down even a little and beat them up a bit). So, it's good for punching power as there's less of substance between your knuckles and your opponent. It obviously doesn't double the shock, it just makes a small difference is all. Anecdotally I feel like it impacts how easily you're able to cut and mark up your opponent too. Horn's trainer is overstating things.