Someone stops the guy from installing unofficial ROM especially in Pixel phone with easily unlockable bootloader? Let's ignore the fact the phone is perfectly

Someone stops the guy from installing unofficial ROM especially in Pixel phone with easily unlockable bootloader? Let's ignore the fact the phone is perfectly fine even without latest security patch even without unofficial ROM. How exactly would someone exploit his phone if he is using newest versions of secured apps? The odds of attack on his phone are next to zero.