Project Treble has been quite a while since Android 8.0 and it makes Android more modular and flexible. Project Treble is a project that when you update or modify Android, the "/vendor" partition gets unmodified and that partition contains all OEM-specific applications, drivers and libraries. So it separates the Android kernel and anything Android from that partition. Because of this, can you flash any device with a GSI image? And solve the issue of users that they want MediaTek chipset drivers to be open sourced? And, I think the "/vendor" partition contains all the drivers so when they're developing a custom ROM or an update, they don't have to rework the partition and don't need the driver to be open sourced. Some people say that they installed GSIs successfully on Chinese phones that are running Android 8.1.