From reading the article you quoted. The reason they don't put it on the label is because they don't use it in the product. They use an alternative, called yeast extract. It appears that yeast extract contains glutamates, of which some are monosodium glutamates. So their labelling would appear to be correct, they label the product they use as an ingredient, rather than the constituents of said product.
Orange Juice, made from concentrated orange juice 35% would be an equivalent label. I frankly have absolutely no idea of the break down of what 'orange juice' is. Its an ingredient, it'll have various sugars, some protein, some fibre no doubt, maybe vitamins, maybe they were lost in processing, but when it says orange juice, they've labelled it correctly.
As Castiel said, good luck avoiding amino acids in your diet, guess we won't be hearing from you around Christmas, you'll be dead long before.
Some products are better when things are used as favour enhancers and to thicken them. Rather than use straight MSG manufacturers found an alternative. Personally I will choose to eat a balanced diet, than worry my existance and the rest of the worlds will end, or my brain will melt to mush because one doctor in American who's peers review his work and disagree thinks it will.
Can't believe we've went from toothpaste concentrations to CTs on MSG.