They all have misses and drips all around them. It's such a simple skill that men can't master even when an entire industry was built to accommodate them.
But you are blasting piss off the porch, the direction is away from you. Almost all of the splatter is gonna end up on the lawn, where you're pissing anyway.
Wood for an outside deck isn't going to be soaking up much liquid, or the deck would turn to shit after a couple rainstorms. It's probably pressure treated