Tyres and bike/rider load

[Blue Hills]

Nonsense - takes a minute or two tops including digging any bits out with blunt screwdriver thingy on swiss army knife.
Most punctures are caused by stuff working its way through slowly.
Have also been known to check mid ride if I go over anything particularly nasty.
When touring I check the tyres every morning.

 

[Twilkes]

I checked some old tyres, and while there were plenty of cuts that looked deep enough to reach the tube, there were at least three GP 4 Seasons and one Gatorskin that had split where the sidewall meets the road surface, so the tube was poking through.

Is there likely to be a reason for this, aside from Continental tyres not being very well constructed?