I think they have a hard time hiring for airside restaurant jobs. It's hard to find and keep people who can pass the security screening yet will still work for low wages.
The last time I was at Pearson, I ate lunch at the Mill St Brewery restaurant in T1 Dom. It was the server's first day and she was very nervous. I also got food poisoning there - 6 hours later and gastro-intestinal hell broke loose all at once.