jtcc/btcc is a ‘saloon’ (aka sedan) race series. Give either a series a google search for a specific explanation. This episode is highlighting race cars pulled from different jdm race series and pitting them against each other for fun.
The 4 door sedan only weighs about 30lbs more than the coupe so it really isn't a big difference considering how much weight reduction track cars have. At least with the accord I know that is the case.
