30 minutes in is a much better one with actual audio clips to illustrate it. I recommend the earlier segments in the program too if you have the time.
20+ years ago I played the lead in a play set in the deep South. About half of the cast was Southern but within a week or so we all were doing the exact same "Southern" accent which was totally copied from Gone With the Wind. We were congragulated by the judge sent to evaluate us for the Drama competition we entered on how well we all matched.
Yes, we dropped the Rs.