I guess it's debatable...? Not questioning your definition, because I've heard and read both, actually, and I've decided to go with this one because I found it more poetic. In Reichl's book, she hears it from a waitress in a sushi restaurant, it's not really her definition (unless she put her words in the waitress's mouth for the sake of narration, that's also possible). So, perhaps it's a translation mistake (since umai means "sweet", "delicious" but also "right"), or maybe somebody somewhere in Japan is taking the piss and is spreading a legend for the lulz, or maybe it's over-interpretation, or maybe the definition has evolved since the scientist in question has named the taste; all I know is that I didn't find that definition only in Reichl's book. But then again I'm not Japanese, I've just studied the language and society for a bit, and I've never even been in Japan, so I guess I'll have to look deeper in that umami thing if I get the chance to find more material. ^^