You are correct, cedar is soft, but so is pine. However, my cedar is holding up very well. I do have impressions in the wood. I would think most wood, when transporting rocks would have scaring, dimples and impressions.
Normally, I place a tarpaulin down when hauling dirt, gravel or sand....I am more concerned with the damage done by my rake or shovel. If I carry metal or heavy stones,I put down a sheet of plywood.
Cedar is a wonderful wood to use in wet weather conditions. You never see folks use pine for roof shingles. It is also used for outdoor decks which are subject to high wear and extreme weather conditions.
Greg