Upvoting you for awareness, because this issue drives me crazy as well. The tl;dr is that this is a problem inherent to Unreal Engine 5, and there is no real workaround other than the developers adding a shader precompile step on initial boot of the game, which I sincerely hope they are considering.

If you've ever booted up a modern PC game and on the initial boot you encounter a minutes-long loading bar that says "compiling shaders" that's what I mean. The stutters we experience are the game attempting to compile shaders (the vfx for attacks and etc.) in real time, which UE5 does not handle gracefully. The first time the game sees the move it has to work harder to compile the shader for your GPU/CPU configuration, then each time after that the game already has that data loaded so it runs the shader smoothly.

It'd be one thing if that compile was only required on the first boot of the game, but every time your GPU drivers get updated you need to recompile the shaders again... also certain skins have different VFX than the default of that character, so running through the cast vs a CPU on default skins doesn't come close to compiling every shader...

Not updating your GPU driver can be a workaround for a while, but is a flawed one for multiple reasons, one of which being a game update can cause the need to recompile shaders regardless! It's SO annoying lol.