You forgot about one simple thing: “unit of hydrogen” isn’t actually a glob of the stuff, but a cell that holds it.
Hydrogen tanks are a simplification - they should contain the same stuff as hydrogen cells, but instead are coded as if they contained the cells themselves.
As a rarely used feature, hydrogen doesn’t get much love. Plasma engines are incredibly rare (1 spawn weight in bank vault - less than 2% chance per bank), plasma rifles barely more common and CVD engines spawn at lab finales and are only used to post-endgame bling.
Don’t hold it to standards as high as the core game everyone plays and knows (and reports/fixes bugs for).
Eventually hydrogen should probably become a separate item with nearly 0 weight, with the hydrogen cell being one of the few things capable of containing it.
You can see how it works in game by filling a vehicle hydrogen tank with hydrogen (25 units is enough), then destroying it and collecting the remains. Entire 2500 units of the remains.
