You're talking about battery cells, but you need to look at the battery _pack_ energy density. The model 3 battery pack, which uses the same cells as semi, is about 170Wh/kg. The numbers in TFA are very reasonable estimates.
(Tesla has typically done better than their peers in overall battery specific energy as well as energy per mile.)
From the numbers I can find, the Model S 85kWh has 7104 18650 cells - if we use 49g for mass of cell, that's 767lb of cell vs the pack weight of 1200lb~, or a very rough packaging overhead of ~36%
This is a naïve analysis but it helps assuage my ego, as I've worked on designs for 26650 based packs where we would have been quite happy to hit 30% overhead :) That being said, I realize people can, and do in fact make more mass efficient packs.