This is a hybrid extension vs antispin in split time same direction, not a polyrythym.
I wanted to offer some clarity for this video. Maybe since posting this you may see this differently?
A polyrythym is the simultaneous use of two or more conflicting rythyms. This is a 4 beat antispin diamond with an extension which starts at the beginning of the 4 beats. So here this would be classed as a hybrid extension vs antispin in split time same direction and is a standard complimenting beat pattern.
To create a polyrythym you would do something like 2 beats on one hand, and 3 on the other, both starting at the same time. So it would create a 1 2and 3 sound. One hand beats at 1,2,3, the other hand beats at 1,and.