History question, regarding Ginther & other Ferrari Yank drivers

I was reading something about Ritchie Ginther and I was surprised to read that when he was let go by Ferrari they had Ginther followed out to the lot to make sure he didn't lift any parts on the way out. I was wondering then, if Ferrari's goal in hiring American drivers in the Fifties and Sixties was more in hopes that if he got one that won races it would boost sales in America but when the American drivers didn't do well, he planned to let them go without so much as a courteous farewell? Maybe I can ask Bondurant that, he drove I think a season for Ferrari and he's going to be at a Cobra event in Pomona April 21st.