I’m no expert but i believe the shaders have to get complied the first time you deploy onto a different platform.
I’m currently developing for android and the initial deploy onto my Galaxy s6 had been “Compiling Shaders 4000” which took a number of hours, but any subsequent builds not require a recompile of shaders.
Similar issue occurs when you go in the opposite direction ( had been launching the game on android and then switched to launch on windows).
After the initial (very long) compile, you won’t have to sit through long waiting times.
Hope that helps/Makes sense.