I would have thought that gravel of any sort will damage the inner tent floor, as you walk on it! I thought that all weather pitches(gravel or hard core) were for front wheel drive motorhomes, so they can drive off without difficulty, or heavy caravans, so they don't sink in too deep and become hard to tow away! I could be wrong though!
You might want to invest in a VERY thick groundsheet(or a piece of old carpet) to use under your inner tent floor. Personally I wouldn't pitch a tent on this unless has NO built in ground sheet.