Ito needs 3 years because the car you saw was pretty much a shell. There will be powertrain development, chassis development, track tuning, crash testing, etc. Of those, the powertrain development is going to take the longest and be the most troublesome. Getting a hybrid system to produce high power under track conditions, be 100% Honda bulletproof under all conditions, and come in at the weight target is going to be a tall order. Plus you have the SH-AWD VSA logic that will need to be tuned just right for all conditions. That means months of lapping and tweaking the software. It's going to be a high pressure development process.