Oh it makes no bloody difference. It can be easier to remove the rear wheel while the bike is upright on road bikes because of how little clearance there is between wheel and frame, but then you still need to set the rest of the bike down somewhere anyway, and keeping it upright without the rear wheel is obviously a terrible idea. The weight of a carbon bike is leaning on the hoods is less than the weight of you leaning on the hoods when riding anyway, worst thing would be a minor hood scratch.