These practices include such offenses as fertilizing garlic with human feces and forms of sewage, growing garlic in sewage
From https://www.mcgill.ca/oss/article/you-asked/it-true-garlic-china-grown-human-feces-and-watered-urine
there is no evidence that garlic in China is fertilized in this fashion. In any case, there is no problem with this, human waste is as effective a fertilizer as is animal waste. Spreading human sewage on fields that grow crops doesn't sound appealing, but it is safer than you might think.
That would be my guess too at first glance. What do they think manure is if they're grossed out at sewage? As long as it's treated properly to reduce pathogens then it's just "ew yucky I don't like the real world".
Also the internet throws a lot of our traditional understandings of culture out the window. A 20 year old and a 40 year old might not have had as much reason to hang out before (although things like sports and hobbies did pull age groups together some) but now they're all playing against each other in the new Call of Duty, sharing memes about Among Us, laughing about how they're too old for the Skibidi Toilet and arguing on Twitter.com
There's lots of injokes and references and slang that I don't understand not because of my age, but because I don't watch Streamer X or play Y game or have Z streaming service. And yet plenty of people younger, my age, and older will get those references because they do. Meanwhile the opposite is true, I've played some online games from my childhood with kids who weren't even alive when the game came out! It was kinda shocking really.