Sort:  

1/3 or 1/4, nothing changes in general. I just made length ratios extreme, and to a numbers which would allow easy divide, and make drawing more self-explaining. What ever those actual length are, guy #1 still holds the largest weight, right?
Or you disagree?

Why would they do it this way? That is done that way just to everyone has the same weight on their shoulders. The rope holding stone stone is in 1/3 not 1/4 of lenght of the stick. I think it is even visible on this picture.

P₂ + P₃ = 100 -> P₂ + (2/3)P₂ = 100 -> (5/3)P₂ = 100 → P₂ = 60 kg -> P₃ = 40 kg
Person 1: 100 kg (he’s alone)
Person 2: 60 kg
Person 3: 40 kg

Your logic is mostly on point, you're clearly applying torque (moment = force × distance) to figure out who’s lifting the heaviest load.

Nicely structured.

SInce I have no better solutions , I think I will agree with you

Nice try If you ask me