The plastic part does have quite sharp edges and sharp ribs on its back. But, as I think Roman pointed out earlier, on- line photos of damage often show the 'leather' split somewhere else, not directly caused by these sharp edges.
Looks to me that when the seat is being upholstered these side panels are stretched quite tight before being firmly fixed to the seat frame . The additional strain when drivers get in and out, summer heat drying out the 'leather ' or extreme cold making it brittle may cause the structure of the fake leather fabric to fail at its weakest point. I have had thin clothing split in this way when put under too much strain
. (Hot sun and bulging muscles of course
,not too much beer and too many pies.
) The plastic side trim may not be helping by concentrating the area under stress into a narrow strip.
I have pre treated mine with 'Turtle wax luxe leather' leather and vinyl conditioner . Too soon to see if this has any benefit.
Word of warning here. I have dark upholstery. The conditioner makes the 'leather' slightly darker, and of course you have to keep the conditioner away from the cloth areas. The result actually looks good and more leather like, but if you extend treatment beyond just the vulnerable seat edges , you may end up having to treat every part of the leather interior to maintain a consistent colour match. .Only then do you realise just how much 'leather' there is ! A job some will enjoy, and some will not. Probably true of other makes of conditioner.
