The fluting looks like an affordance to attach a spear stem or arrow stem to. To my admittedly "know nothing" self, calling it a shock-absorber might be over-thinking it.
The flute may well have been intended to make the head easier to attach, but that's not the point. If such a head were brittle and failure-prone (per the hypothesis in the article), its users would have collected less food and left fewer descendants to use their particular favored technology.
The fact that the technology was pervasive and widespread means that it has some clear advantage. And it's the advantage the archaeologists are looking for, not the intent. And it turns out, I guess, that such heads turn out to be less fragile on impact because the longitudinal force is better distributed. So these heads are more likely to drive deep and deal a fatal blow, leading to more food for their users and more children to instruct in spearmaking, and ultimately more spear heads in the archaeological record.
Engineering implies forethought. If they didn't want to imply forethought, they should have used different words.
It acts as a crumple zone, like we have in cars now to protect occupamts in a crash. For the spear points, the fluting "crumple zone" protected the important cutting edges from breakage. The shaft would break loose at the fluting, damaging a small amount at the butt of the stone but allowing the main body to be reused.
Without fluting, at a hard impact the breakage was more likely at the tip, ruining any potential to reuse the point.
probably they just had more food and resources on the new land so a distinctive traid on the tools that is status only could be aforded by most of the community.
imagine someone looking 500 years from now at us. They will see all the expensive cars in LA and bay area and wonder why those two societies needed such larger engined while all other societies had smaller ones. I'm surr they will inspect the remains of all those BMWs and find practical advantages over a fiat, but we all know it was chosen just for the looks and disposable income.
I bet it was the same with the spears.