Render Selection that actually works on yellow clips

That simple.
Maybe have the another command for render selection effects only if you want to distinguish it? I don't think many editors use the effects only render though, I think the mayority just renders all.
The yellow clips preview when using Optical Flow, for example, isn't good enough, it show jerky. You need to see them fully render in green to see them properly. Same as the time remapping effects.