Why do you assume it's people leaving because of cruel conditions and not people being fired, especially given that they're open about firing lots of people and encouraging many to quit? They don't hide the ball on that.
Because they have calculated that turnover is more profitable than the cost of quality recruiting, training and on boarding. Firing people is super costly. The math of the churn and burn model is working.
Do they create high turn over because they’re selecting for the best people to exploit?
It’s a gestalt, you can see it two ways and I have no clue why someone would want to see it as a “good practice” unless that view was beneficial to their job and career advancement.