The difference is that you fill up these cars with water and the H2 is produced by the car. The breakthrough is the rapid production of H2 from water.
my guess is they figured out some production/consumption rate ratio and have a separate chamber to convert small amounts of water to H2 as its needed. The expansion from water to H2 would provide the pressure to push the H2 to the distribution system and they use dual port and direct injection to cover some compression and power issues along with a turbo to reintegrate the oxygen with the exhaust.
according to the article, the biggest breakthrough was in maintaining a constant temp with their water-cooling system
I haven’t read anything from Toyota directly that says they have an actual working water engine that produces hydrogen on demand.
I’ve only found information from them directly about the Marai.
