When I read the bit in McGill’s piece about lean from the pelvis enabling forward momentum my first thought was the quote from the iconic short film 13 seconds
“The head is the healm. The pelvis, the springboard.”
He’s pretty upright and bent lumbar during some of the slower speed slow motion type shots, but some of the track film where he’s full speed and race film you can see better lean and that wonderful action of the trail leg off the hurdle. He also had that unique annamoly/outlier trail arm that blocked much earlier than most elites (in front of the body even early in the race).
Guy did a lot of gorgeous and very effective things in the hurdles in the 70s. Always loved his trail leg and general relaxation and rhythm.