Free range spitting...in the wind., page-23

https://www.dairynz.co.nz/farm/the-5-production-systems/

This article is from across the ditch and is a guide only but it does show the various degrees of shift of feed type from paddock based grazing on growing grass to importing feed from other sources. This has more impact on your milk quality than anything else assuming everything else is normal.

Free Ranging cows can still be fed imported feed (e.g. grain or licks) using silo troughs in the paddock and conversely grass grazed cows can be eating the completely wrong diet straight from the ground if the paddocks are sown and managed and fertilized appropriately.

Intense farming can offer cows better climatic in some circumstances and the feed can be freshly cut grass from nearby feed paddocks or conversely it can be remote unrecognisable feed that is imported from distant location.

Don't confuse their diet (Grass Fed) with their exercise (Free Range)....same principle as applies to humans.