Wait, what? Not sure where this idea came from, but no, that’s not what happens , LOL. Many working ranches provide decades of evidence.
My horses live out 24/7, I didn’t build stalls because I have no interest in cleaning them & I have an actual job. I can close off part of the runin shed if needed. My daily necessary chores take about 10-15 minutes. (disclaimer: I purposely dont live where it snows often, we get only occasional snow)
My horses are not “feral”, rofl, they come greet me for every meal. During which they are groomed (unhaltered while cleaning feet, the horror), inspected, etc. They have excellent manners and I go fetch and ride them whenever I feel like it. They also come greet me whenever I go in the pasture. Because I have built a good relationship & I make the terms of our agreement fair & clear.
Horses do not “forget” training simply because you don’t put them in a box every day, feel free to do what works for you.