I was watching this short video on little-known things about the original Metal Gear Solid, and you hear one of the lines that he changed--and a ton of players, myself included, probably never heard this particular line until now.
The "onion" line was not in the Japanese--and by extension, is not in the Twin Snakes version. One of the top comments on that video talks about additions like this being why he was fired. The story seems to track, as far as I can tell.
Later games stuck much more closely to the script. Maybe a little TOO closely, like MGS3's Volgin mumbling "Kuwabara, kuwabara..." even in English.
If only more creators had this kind of balls.
Though if anyone cares, here's an article on the localization, written by Blaustein himself. Archived, of course.
Little over 2 decades ago I used to translate anime for fansubs, and I always tried to do as direct a translation as possible, mostly to help people learn the language. Hearing/reading the same spoken/written words would help watchers pick up the language was my belief. Mostly because that's how I started learning.
Of course even then I had push back from the 'qc/editor' who wanted to use colloquialism. Quit with the series these clowns were on and never went back. Those were the days of fansubbers hanging around primarily on IRC.