We came across this cutaway photo for a 2012 Honda N One micro van that the company offered in the Asian market.  It shows a fuel tank mounted under the front seat and claims that the feature is patented.  It’s hardly original thinking on their part. 

    Honda N One

Citroën located not one, but two fuels tank under the front seats in the 2CV Sahara.  Not exactly the safest place to locate them as they were literally under driver and front passenger separated from the occupants by merely the seat fabric, but that allowed Citroën to fit an identical engine and gearbox found in the front of the car into the rear, making it not only a true 4 x 4 but one equipped with 2 drivetrains that could be operated independently to give a FWD or RWD only configuration if need be. 

        2CV Sahara

In Honda’s case, their claim of a unique, innovative “Center Tank Layout” patent served to free up space in the rear, and in later models, such as the HR-V introduced in 2016, allowed rear seats to fold into the floor letting a 185cm-tall adult sit comfortably. 

    Honda HR-V

Honda had the presence of mind to separate the tank from the passenger compartment by locating the tank under the floor panel.  That in itself may well be the reason why Honda’s patent was granted.  As far as we can tell, this is the patent they are referring to:

https://patents.google.com/patent/JP2000085382A/en?q=%2c+fuel+Tank%2c&q=Center&assignee=Honda&oq=Honda+%2c+fuel+Tank%2c+Center