Bolstered seats don't take kindly to dragging / sliding yourself into them unfortunately. You kinda have to climb into them to avoid this kind of wear/damage, but unfortunately your Dad isn't fit for that. MK5/MK6 GTI seats were notorious for premature wear on the bolsters. They'd be in bits in no time if you weren't being fairly careful.... very common to see MK5/6 GTI's with holes in the bolsters.
VW would probably tell you that the whole seat cushion has to be replaced but a decent upholsterer / after-market leather fitter should be able to sort that without having to replace.
I'd also agree with what somebody else said above - the cloth seats, particularly the bolsters and the material on the door cards - is crap IMO. It's the main reason I'd personally spec leather / art velours in the car - the "pleather" you get on the door cards isn't wonderful either but at least it wears very well.