Actually the quote rather ambiguously said they used meth to "numb fears," not to "numb senses." It's a peculiar terminology, but your claiming that meth numbing senses is bullshit is something else again. You made up that claim then said it was bullshit. I think, but am not sure, that your further implied conclusion was that the article's claim they used meth at all was therefore also bullshit.
It's easy to grasp the concept of morphine or demarol as inducing a laid back euphoria which would diminish the fear of crashing. It's not so easy to see meth as "numbing fears," although it could make one braver, and certainly more alert and accurate.