Question for you guys

The converter is pushed forward under pressure. One reason the crank thrust bearing wears in the rear foot braking a car. They may have added the washers because the thrust bearing is wore. This will prevent the converter from coming to far forward under pressure.

Many things to consider here for the reason of the washers and all responses so far could be correct. In all my years never installed washers behind the flex plate. I also never removed one with washers in there.