I'd be interested in seeing a source for that less than 3% number.
However most cattle are certainly finished on grain without a doubt. Grain that could possibly put to better uses (or not grown and save the fuel and water).
So they go through the feedlots but most cattle are not in the feedlot at once (feedlots are a smaller part of the time a cow is alive, some months only).
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.
I think it's a pretty huge point that's overlooked, not just a 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!".
Here's another one:
https://www.reference.com/pets-animals/cows-eat-a677816334f1...