I have not analyzed this kind of phenomenon earlier so we maybe need iterations and some help.
The music itself is quite heavy here compared to a flute concerto!
According to my earlier ideas about heaviness it includes musically late steps and a deeply relaxed body. Only the spine is striving upwards and the rest downwards.
I have reviewed the video only up to the painful gancho so my thoughts are for the first part.
The timing of steps and adornos here gives me a feeling of that these actions are creating the accents in music. I downloaded the video and when reviewing it at slow speed I found how his forward steps are not marking the strongest accent with the heel but by the ball of the foot.Note that the heel hits the floor first. At normal speed the visual impression must be that the whole foot is marking the accent. This could be part of the heavy impression.(with reservation for the fact that some cameras/video converters can unsynchronize the visual/audio connection)
I think they had some sections trained before and the rest of the dance was improvised. But I could not found any hesitation or misunderstandings; they were all the time comfortable with each other and with the music. They must share same type of understanding of movements and this song.
When teaching I usually talk about the need to have your body tension to be al Tango in the same way as the spagetti needs to be al dente! She was doing that fantastic well here! She had controll of the body without visible tension, movements were flowing without hesitation or rushing with pleasant timing with his movements and the music.
There was a seamless flow with his and her movements and the music.