Evolution will "make use" of anything it can, even and perhaps especially factors that no intelligent designer would ever consider.
Related: What intelligent designer would situate a pleasure/reproduction area through a waste disposal zone?
If there was an intelligent designer, he either had a weird sense of humor or didn't feel like putting in too much effort into his job.... Oh dear lord, God is Wally!
Do you need to speak with someone about the birds and bees? You seem to be a bit confused. Waste would be solid waste whereas urine mostly sterile if no infection is present.
The genital area in humans would be in the front for both sexes. Waste is handled in the back.