I suspect I'm not the only one who sees a grain of truth in Guede's stories. He's lies are self serving and he tries to incorporate into his story the evidence he knows he left behind. Thus he admitted sexual contact, the bloody towels, the visit to the bathroom, the time of death etc.
I don't think he scrubbed off anything to the point of leaving his own DNA.
I think he just rinsed himself under the shower head. And any trace of it in the shower had been washed away. The traces in the sink, bidet, on the side of the toilet are, let's say, secondary spatter, the remains of him operating there with blood on hands and clothes.
I think you are wrong in expecting more blood traces in the bathroom left by him. Look how little blood there is in Meredith's room apart from the places where she directly bled or exhaled blood onto surfaces. For example the bed cover where Guede sat to go through her purse has just two or three isolated blood traces. There were more blood droplets in the sink alone.