I can't confirm or deny the dark edges as a feature, but you might try a [https://androidforums.com/threads/moto-z2-play-how-to-force-reboot-or-restart.1185861/|force reboot or restart] and see if it goes away. I'd also make sure the screen is fully back into place like before the repair (with respect to the case/rest of the phone), ie no excessive gaps or strange bulges.