The only reason a multiplier is used at all is to make small numbers bigger so people used to seeing a number larger than 1 are more comfortable reading. Neither 40, 70, or 100 make more sense than the other.
I said 40 because I brain farted on mintutes. 100 is purely arbitrary at the cbb level. At least 70 would give another usable number because it shows what someone would score if they played the whole game (like era) rather than just a random multiple of the ppp. If you really wanted to do that you could just revise the per multiplier each week based upon average possessions per game.
Not criticizing the presentation, just curious where the number came from. That's been answered. TY