I don't think any reasonable person expects the price of the 2-door truck to be $21500 when it finally is produced. That price is guaranteed to rise between now and the delivery of the first vehicle in 2028, it it ever happens. For potential customers it is a signal that they are committed to delivering a quality vehicle at a low price point. If you read the privacy policy, the reservation agreement, and payment terms it is all laid out in plain english.
Once they get vehicles on the road and a dedicated owner base they can determine whether there is interest in a hybrid drivetrain model. I understand why they aren't offering it right out of the gate. I do expect that they would be willing to consider it in the future should they ever make the leap from marketing vaporware to manufacturing.