Will this upgrade makes your driver's bottom seat tiltable?
The assembly in the 2018's do tilt. It seems you would have to buy the whole thing.
If the only option is $4300 and you feel tilt is critical to your comfort, It would probably make sense to just upgrade and trade in for a 2018 or wait a little but for a 2019. While you would take a financial hit, you'd be getting numerous upgrades instead of wasting all that money to replace an otherwise working seat.