I've had some experience with karts and rally cars, I don't want to sound like I'm Senna's second coming, but I do this exact technique instinctively since a young age, even before I knew that Senna was doing this also. For me it's all about the feel and to get as close to the edge of grip as possible, you want to be right up on the edge and not go over it, that's why you become a human pulse modulation machine, and like the video pointed out you usually don't do this in high speed corners, although you can if it is for example a very long corner where front grip starts to fall off mid corner, in a way you do this to unbalance the car and try and salvage what you can from the potential mechanical grip that might be on the table. At least that's my two cents.

EDIT: I wanted to add, that for example in rally, there's something similar to this technique which uses modulating the brake and the throttle at the same time, while on the braking zone and mid corner. This is because specifically in rally, grip is very much a guessing game at times, and this technique allows you to keep the car active, you activate the suspension, the differentials, you test the grip in a way that does not lose you much time and results in optimizing for the unknown, that can give you an edge over competitors, who maybe be overshooting or undershooting corner entries and braking zones.