This experiment is not really "lesser known" as the article claims. It is known by everyone in physics, because it is so fundamental. And fascinatingly simple in the concept of the setup to prove a quantum effect.
To the public, perhaps it is "lesser known" but so is all that isn't CERNs LHC or Einsteins theory of relativity.
Yeah, the article says, "It was indeed one of the most important experiments in physics of all time". Presumably the "lesser known" applies to the lay public, who know schrödinger's Cat (a thought experiment, not a lab one) and maybe the two-slit experiment. The concept of quantum spin and its demonstration is less well known to non-experts. I'm certainly no expert, but the concepts of spin, probability amplitudes, and bosonic vs fermionic behavior fascinate me.
Even then, the vast majority only knows the _name_ of it and something about the cat being both living and dead. I doubt many people could even tell you it is an experiment, thought or otherwise.
To the public, perhaps it is "lesser known" but so is all that isn't CERNs LHC or Einsteins theory of relativity.