What is the ruling on urine splashback reaching the one performing istinja' from the concave toilet bowl of an Arabic-style toilet?

It appears that the questioner is afflicted with waswasah (obsessive whispering), and we ask Allah to grant him well-being and healing. Rulings often do not benefit those afflicted with waswasah unless they treat themselves. This particular issue makes it easy to avoid waswasah by pouring water over the remaining urine in the basin once until its trace disappears, then performing istinja’ (cleaning oneself after relieving nature). The water that splatters after the trace of urine has disappeared is pure. Alternatively, one can move away from the basin and then perform istinja’ with water, or forgo water and perform istinja’ with a tissue or other materials that do not cause water to splatter.