I fill it up to the neck and DO tap it down several times on the way. I'm not saying that mine is the right way but it's just the way I do it.
Just a guess here but is a looser fill of more benefit if the water is gushing through it faster - i.e. at the point of use ? Apart from rare occasions, my only use for resin is after an RO so the flow is much lower than at the point of use.