because they are the only devices on the market that allow locking the bootloader after installation
AFAIK on Xiaomi Mi A2 lite if I flash back the stock fastboot ROM (I had it do it once because I crippled the partition images (this phone is A/B partition device)) it locks your bootloader and you have to unlock it again. I don’t know if this applyes to MIUI/Hyper OS phones too, because Mi A2 Lite uses near to stock Android.
AFAIK on Xiaomi Mi A2 lite if I flash back the stock fastboot ROM (I had it do it once because I crippled the partition images (this phone is A/B partition device)) it locks your bootloader and you have to unlock it again. I don’t know if this applyes to MIUI/Hyper OS phones too, because Mi A2 Lite uses near to stock Android.