I too am missing the punchline. Sounds like synthesizing hydrocarbons directly would probably be simpler and would not require changing any existing infrastructure.
While the 'used' oil is being stored, to be 'reloaded' with hydrogen by whichever means.
So the 'carrier-oil-component' is the reusable thing here.
All while being able to be handled, stored, transported similar to diesel.
Supposedly.
shrug