If it's a rear hub motor and you throttle only the chain is not even involved in the bicycles movement. In fact you could remove the chain entirely from a rear hub motor and still have full power and throttle assist no chain is necessary.However, I would say the drive train (especially the chain) will always wear faster when started in high gears (disregarding if it is the mid-drive or hub-drive motor). Only the strain with the mid-drive motor will be significantly higher.
You could essentially remove the chain , the pedals , the front chain ring , the cranks , the rear cassette from a rear hub motor and the bike will power forward as normal with the throttle.
Remove the chain from a mid-drive and you will not move an inch.