Granite Step Foundation

I am having a paver patio installed by a contractor and he will be using a 8" compacted gravel foundation to support the pavers. Additionally, a single granite step (48"x18"x7") will be installed. The contractor says he needs to pour a 6" concrete foundation with the same footprint as the step in order to prevent the step from settling over time due to the weight of the step. However, I think the step should be placed directly on the 8" compacted gravel foundation. Do any of you think the concrete pad is necessary?

Thanks,

Chris Miller, P.E.