I am not the person who wrote that comment above, but they did not say "90% of soy" -- they said "90% of that soy", referring to soy grown in areas of tropical deforestation.

I have no clue if the assertion is correct.

Edit: FWIW, it appears that US soy is mostly used for livestock:

> Just over 70 percent of the soybeans grown in the United States are used for animal feed

https://www.usda.gov/sites/default/files/documents/coexisten...

And globally, even a higher percentage:

> About 85 percent of the world’s soybean crop is processed into meal and vegetable oil, and virtually all of that meal is used in animal feed.

https://web.archive.org/web/20170112075924/http://www.soyate...