grub-boot-success.service set the boot_success=1 in /boot/efi/EFI/rocky/grubenv

Want to know what is the relevance of this boot_success=1 in rocky.
Please provide more detail on this.

If boot_success=0 it means that the last boot was not successful and it will show the grub menu by default. When it’s 1 the last boot was successful and proceeds as normal, typically without showing the menu.

Is that only for grub menu or is there any adverse effects is its boot_success=0

It only shows the menu with the default count down (5 seconds) before booting the selected item, just as grub has always done before.