If you're accurate enough not to pee on the counter then the only thing holding back someone so inclined is the social taboo. It's not like the kitchen sink where stuff regularly goes in there. Does pee harm pipes? Will it make the sink bowl radiate a permanent smell? I just hate wasting water by flushing only pee but also don't like letting pee sit for an excessively long time.
imma stop you right there, the amount of water regular people use for sanitation is wholly necessary & a pittance of industrial costs and wastes. your entire life of water use is an accounting error at a commercial enterprise. do not let yourself be shamed into unsanitary practices by people who fucking GOLF