Game Mechanics: Weight / Encumberance

[Tracktrack]

A Stacked item weighs the same as a single 1.
Never noticed this before with only every having dots/food/water at 0.1 a piece.
But when playing an alt and collecting small mammoth tusks at a weight of 3.5, you can stack 20 at 3.5 or individually separate them for 3.5 each.
Is a stack of 20 not suppose to be 20 x 3.5 in weight?

Also just broke down the stacks of water and food and they have the same problem.
1 stack = 0.1 weight, instead of 20 x 0.1