I think that the major issue with the bootloader is when a user confuses the device file for the entre drive (/dev/sda) with the device file for the partition (/dev/sda1), whch is not entirely unreasonable for a new user who doesn’t understand the naming system to do. Like, mkfs.ext4 /dev/sda rather than mkfs.ext4 /dev/sda1. Then you overwrite the entire drive, starting with the MBR, rather than the contents of a partition with your new filesystem.