I haven't completed a power level list in many years, but I recall it having to do with two possible things.
1. Gero's calculations. Gero thought that absorbing two weighted Piccolos would be enough to beat Super Saiyan Vegeta. He also thought that absorbing one weighted Piccolo, plus Gohan & the humans would be enough to bring him to that level.
Chapter: 345 (DBZ 151), P14.7
Context: after seeing that Gohan, Tenshinhan, Piccolo, and Kuririn had followed him
No.20: “If I collect their energy and add it to my own, I’ll be able to win against Vegeta!”
Chapter: 346 (DBZ 152), P8.2
Context: Piccolo wants to fight No.20 without Vegeta's interference
No.20: “Don’t interfere, he says…Kukkukkuh…Alright, if I drain [Piccolo]'s energy again, then [I’ll win] against Vegeta…”
It's tough to make sense of this when Base Vegeta is established to be >> weighted Piccolo.
So unless the Super Saiyan multiplier shrank, it's hard to rationalize Gero's calculations. Of course you could take the stance that his calculations were simply incorrect.
2. This one is more of a preference thing than anything, but it's easier to have Base Goten/Trunks around Android 18's level with a reduced multiplier. This naturally goes for anyone on that tier, such as Cell Games Goku and Boo arc Teen Gohan. It's not impossible to go with the 50x multiplier but I always found it easier to do otherwise.