the feature never existed in UE3 either and yet the shadow acne issues were acceptable, in a state comparable to other engines (which isn’t the case here)
Shadowmaps were introduced in 1978 and Cascaded Shadowmaps were introduced in 2007. That doesn’t mean that in 2017 you can in UE4 make a big scene with fully dynamic lights using CSM with Skylight + DFAO, and then dance happily about the performance.
My point being that adding more features that have ‘some’ cost (i.e. PCSS, contact shadows, POM or tessellation, to name a few) on top of other features that already have a fair cost, isn’t exactly going to be forgiving with performance