heat moulding?

my jackson freestyles fit me perfectly, but the seller says i must heat mould them by putting a hair dryer on medium heat inside the boot for 5 minutes, then put skates on as if i'm about to go skating. just did that to one boot and honestly don't see the difference (skated in them once). i ordered online, closest shop is 3 hours away. do i really need to heat mould or not?