My granddaughter was doing medical research in college...and she said all the foreign students never spoke English in the lab.....except as absolutely necessary. She got to be VERY distrustful because of it.
I worked in medical research too, and there was one Chinese doctor that we all swore was a spy. Very little English, and he was a jerk. This was in the early 80’s. One time he just up and moved my experiment that was in process and took over the space. I wasn’t in that room for about 30 minutes so that I could prepare the next step of the procedure in another room. When I got back to check on my work, I found that he had moved my materials completely out of my work space, and set up his own experiment instead. I was furious! I completely lost it, and yelled, and went to my boss to tell him that now we would be behind schedule. I had to start everything over. I was 2/3 finished with my project! Luckily, I was able to reschedule rooms and equipment necessary again and got that portion of the experiment completed within a couple of days. I really gave that doctor a scolding, which was funny because I was just a tech and he was a visiting Ph.D. About a week later, he came back in my lab space with a silk scarf. I told him he didn’t need to do that, a simple apology was enough, but he insisted and my boss said I should keep it, so as not to offend, so I did take it home. I don’t think I ever used it. After a few years, I finally donated it. Anyway, yes, I agree with your granddaughter. It was hard to trust someone who wouldn’t speak English.
I used to always think my Chinese in-laws were talking about me when they would speak Chinese at the table and ignore me. As I learned Chinese I found out I was right.