Like everything, the proof will be in the pudding - hopefully this will be implemented as a trial for potential users and a free update to existing users, so that both can try before dedicating resources to yet another HDR workflow.
It is not so easy to tell from the video if the first set of adjustments creates a flat image with obviously overcontrasty edges because it is a preview and not viewed at 100% or because that is what the image actually looks like after making the adjustments. I'm not sure why the choice was made to drop the exposure (the midtones in most of these apps) instead of bringing the highlights down. Many times highlights and shadows controls have spatial ranges in which they operate, making haloing and similar artifacts apparent the more they are pushed. Maybe that is what happened here, or maybe it is simply a byproduct of the scaled preview.
It is pretty apparent that OneOn is creating a clone of Lightroom, with the ability to use layers. In fact, that is what most of these all-in-one raw converter/editors are trying to do, with some sort of ability to add "filters" and "effects" non-destructively.
Variety is the spice of life, I suppose.
PS - Of course, contrary to the narrator's opinion, one can capture this scene in a single exposure - you just use a Grad ND filter. It is just another method of tonal range compression.