This seems fairly standard for phone interviews at large tech companies, regardless of the age of the interviewee. The interviewer is probably an engineer who

This seems fairly standard for phone interviews at large tech companies, regardless of the age of the interviewee. The interviewer is probably an engineer who had to find a random conference room to conduct the call in (hence being 10 minutes late and using a lousy speakerphone). Asking the interviewee to talk through the code he's written would not be unusual if the interviewer wanted to find out about the thought process that went into writing the code. And it's impossible to know without context, but the "barely fluent in English" part sounds more like bias on the side of the interviewee than anything.