So I was trying to look up dosage since that seems to be the only thing missing in this thread, and I came across two things.
One is this arbitrary experience, hear say technically at that, on the results of adding MSG to pots of cayenne peppers
TLDR; They found that adding MSG as fertilizer to the pot(s), neutralized the heat and possibly the flavor of the peppers. The MSG fed pots were not hot at all, and the pots with no MSG were still hot. I haven’t been able to find any other experience like this so far in a quick hunt.
And then this other paper I found does list some dosages(4ml/liter and 8ml/liter… Unsure how they’re getting milliliters out of a dry powder 
) against and with standard fertilizer, but doesn’t properly account for all the statistical differences for each result they show with their graphs.
https://eksakta.ppj.unp.ac.id/index.php/eksakta/article/download/283/152/1448
They also don’t actually eat said peppers so no idea if the effect from the first site is a thing or not.
On another note, it seems MSG breaks out to NPK. It seems you can feed a plant solely with MSG and no other fertilizers at all.
MSG can be used as an organic fertilizer because it has a high content of organic matter and nutrients such as elements N, P, and K. This is confirmed by research using MSG (Monosodium glutamate) with an optimum concentration of 15 g / plant, which states that MSG contains 5% N elements, P 0.4%, and K 1.7%, thereby increasing the production of pakcoy plants [37]
So from this site and paper and the previous papers posted in this thread, that science project lol and some quick research; I’d wonder if any “benefit” of MSG is solely because of it’s NPK ratio and easy uptake, and not some extra function(s) we haven’t uncovered yet/aren’t happening in our other fertilizers anyways 