But it does. This news is years old. I agree, security is a thing. And good security has layers. The idea behind monitoring (post boot) of your /boot partition is to be alerted to any unexpected changes.
For a threat model involving “glowers” with UEFI a based system my primary concern would actually be in the CPU frontdoors before I spent any significant time worrying about the bootloader. But then again, I’m using neither UEFI or GRUB.