Read steady butt CPM as a tip-mass clue
The instructor explains that one way to make a shaft stiffer is to add more material, which thickens the wall and drops the torque a little. With the butt-section CPM unchanged, the instructor reads that as a sign the maker is probably adding the shaft's seven grams of extra mass to the tip section, producing the extra stiffness.
Channel: Club Champion
Watch official source at 12:09Why this context matters
The instructor is inferring how added tip mass likely creates the shaft's 'high' and 'low' stiffness options, based on the unchanged butt CPM.