I faced the same issue! The 2018 does not offer TrueTone support the 2019 & 2020 models have. The cable connection is not the same. You need the correct display and you may need to replace the key bd backlight fuse.
To add to this the 2020 model lid is mounted slightly higher for the newer keys as this was the first system to get the still newer scissor keys from the Butterfly keys. So using a 2019 display will allow the keys to rub the screen.