I've had a tire like that, it had been run tubeless and when I mounted it with tube it got pinhole after pinhole from accumulated thorns.
I've also discovered an unintended consequence of heavy duty urban tires is that small stuff can hide in their thick tread and cause a slow leak. I rode for 3 days with a hunk of glass in my tire before I realized it was there because I just topped up what I though was a slightly porous tube.