I have not read the whole article so apologies if this is touched on but is "discovered" really the right word here? The foods and molecules that have this flavor were already being consumed long before the term was coined.
This was the scientist that not only hypothesized that umami was a "basic taste" with receptors directly on the tongue, alongside the west's 4 well studied ones (sweet, salty, salty, bitter), but went on to prove it.
(His work actually puts the other four "basic tastes" to shame because where those four are mostly "well studied" in the social sciences [psychology tests of where on the tongue most responded to each of the 4], he actually narrowed down the specific taste receptors for glutamate, and how they operate.)
I think that it's an acceptable use of the term. Even if people consumed it before that, if they weren't aware of it then its existence could still be discovered.
It's along the same line as "Isaac Newton discovered gravity."
(His work actually puts the other four "basic tastes" to shame because where those four are mostly "well studied" in the social sciences [psychology tests of where on the tongue most responded to each of the 4], he actually narrowed down the specific taste receptors for glutamate, and how they operate.)