If you experience damage or fretting on the shaft or sleeve under the rubber boot it means that the boot did not attach its self to the shaft. The faces had stuck together and you were sealing between the stationary rubber boot and the rotating shaft. In many designs the carbon can be installed backwards and often is. The problem is caused by the seal packaging method. The never tell you to turn the carbon face around at assembly.
Mechanics usually install hardware the way it came out of the box.
There is nothing in their experience to tell them to do it differently. The most common failure with this seal is to rupture the rubber bellows and experience a sudden and massive bellows failure. Well designed, balanced, O-ring seals tend to drip excessively when they begin to fail. This bellows design leaks massively at failure. There are much better elastomers on the market for a wide range of chemical compatibility and operating temperature.