because only the murmuring makes the difference!
without murmuring you don't have a mealtime ray-tracing rendering.
realtime raytracing always mean skip the rendering means skip to lowering the murmuring to send the data to the screen but you can set the FPS rate complete arbitrarily! 100fps or 1000fps it just doesn't matter!
the only point that maters in ray tracing is: the murmuring rate slow hardware means high murmuring fast hardware means less murmuring and its NEVER without murmuring if someone claim raytracing without murmuring then its a offline renderer and not a realtime renderer!
here in this video you can watch the murmuring all the time and the FPS rate dosn't matter: