Given that the main alternative to the Kurgan hypothesis, the placing of PIE in the Anatolian highlands, has major problems with timing and the distribution of later languages, my sense was that the Kurgan / Yamnaya hypothesis is pretty widely accepted these days even prior to this sort of evidence.

But, yeah,when you come in with fire and sword on an essentially immobile population, probably moving your own population in behind the front wave in wagons, the net effect tends towards overwhelming the prior population, especially when this is the first time this has ever happened. When you add in status effects over the next few generations,the proportions can only increase.

And, if course, this isn't like the Huns,sweeping over Europe in one lifetime. The splintering of PIE in Europe into Celtic, Italic, Germanic, Hellenic, Lithuanian et al. argues for a gradual inundation, like the tide coming in.

(Edited to reverse autocorrect errors.)