His "formula" is the wrong one for the R suspension.
It is correct for the X.
For the R use the anti-squat calc shown here:
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View attachment 206060
This is a simplified approximation that neglects a few factors, but it is an easy place to start without several advanced degrees.
The lower link is the lower blue line, the upper blue line follows the front half of the upper A-arm (not the pivot axis for reasons I am not getting in to here).
Still bucks but not for the reasons in the video.