TFA said it: "America gets 97 percent of its beef from feedlots."
Here's another one:
https://www.reference.com/pets-animals/cows-eat-a677816334f1...
Here's another one:
https://www.reference.com/pets-animals/cows-eat-a677816334f1...
The largest number of cattle, currently, if you counted them all up, are still on pasture.
Not that this detracts from your point, mostly a minor semantic quibble.
If a group of kids were fed healthy, home-made meals all week and then get a piece of chocolate cake on Sunday night, it's clearly misleading to say "100% of these children were raised on chocolate cake!".