I did not doublecheck your calculations, but they are probably right.
The decision to go this way was not because of energy density.
It was more of a safety and economical decision (don’t remember exactly, but you can recharge the Li-Ion probably a thousand times - you can’t do that with the Lipo’s).
The original thread as to why I am going this route is here: How about 18650 Li-Ion battery pack over the Li-Po packs?