I am aware that Linux systems largely use GRUB 2 as the bootloader stored in the master boot record of a GPT hard disk. However, each partition has its own Volume Boot Record or Partition Boot Record, and from this link, I found the following information
Boot sectors are the first sectors on a hard disk partition, except in the case of extended partitions, which are just containers for other partitions. Boot sectors offer 512 bytes of space and are designed to contain code capable of launching an operating system on this partition. Boot sectors of formatted DOS, Windows, and OS/2 partitions do exactly that (in addition, they contain some basic data about the file system structure).
In contrast, the boot sector of a Linux partition is empty (even after creating a file system on it). Thus, a Linux partition cannot bootstrap itself, even if it contains a kernel and a valid root file system. A boot sector with a valid start code contains the same magic number as the MBR in its last two bytes (AA55).
Why doesn't Linux write anything in the partition boot sector?