If you don’t have issues with booting your system then no, this is not what you need to do.
So please disregard the rest in that case.
As far as I can see, his information is incorrect anyway.
He did chroot into the system, but then proceeded to use /mnt/boot as the target directory.
From within chroot (where he is), that directory is not /mnt/boot but /boot - the parameter is not needed.
This would be the way to do it without chroot.
and
The command is now different - it’s manjaro-chroot now.
But I could be wrong.
I’d rather go with this information here - or look in the wiki how to chroot