He's Scottish - we use the word folk a lot up here, in normal conversation about normal people doing normal things.
Eg
I'm going to my folks for the weekend (I'm going to my parents house)
Everyday folks, doing everyday things.
It MIGHT be an adoption of the American phrase by him, but I wouldn't discount it being a perfectly normal word for a Scot to use instead of "people".
I like it in my context, and refuse to allow its association with the rainbow mafia to steal it from me.