The wear on mine was a little further towards the sidewall, kind of on the 45 degree angle between the main tread and the sidewall. Closer to the one on the left picture. My first went at 12500 miles and literally wore right through and failed when there was 5mm left on the main tread.
I do drive over about 5 speed cushions similar to those in previous post each way on my 3 mile commute to work each day. I guess thay may not help!