I’m not excusing it, but it makes sense technically because we can’t directly execute the D3D shaders, and converting it just-in-time could cause initial stuttering. It’s a kind of vendor lock-in in my view, and some translation step is needed. Steam even goes a step further and tries to ship you pre-compiled shaders, but it’s not perfect and especially games that update often can end up generating the shaders locally on a regular basis.
I’ve definitely noticed this, but it hasn’t stopped me from enjoying my games so far.