Often when I launch a game through Steam that “processing Vulkan shaders” window appears and loads for a couple minutes. Sometimes it takes no time, sometimes it takes several minutes. But then, for larger games like Dune Awakening or Outer Worlds 2, the game needs to sit and process shaders for another couple minutes anyway. But for some games, like Enshrouded, I can skip the Vulkan processing with no problems in the game (I do that because the Vulkan processing doesn’t go anywhere). So what is that Vulkan processing for?
If shaders don’t get preprocessed, then a lot of the same work has to happen later, it just shows up as a seemingly random frame that takes particularly long to render.
(edit to add:) or a section where some of the rendering doesn’t look quite right initially, if they do asynchronous rendering.
In the limit, the sum of all these delays can add up to the same amount of time that the preprocessing WOULD have taken, but you also don’t necessarily use every shader every time you play every game, so YMMV.