Swapping motor on Plarail Nagasaki 2x series 3000

That's a weird little train, why did they go for such a design? Why didn't they just do their normal 4 wheel carriages with normal type connectors, its not as if Tomy usually care too much about realistic scale

If it was a big deal they could always have made the front/rear carriages just shorter than usual, after all the motor is in the middle car...