This is only for compile time, for packagers.
It is both.
Neither grub, nor Arch packaging should let systems unbootable, because of one new variable introduction. Ask bashrc xinitrc devs how they do it.
When a commit breaks backward compatibility, a new major version is required.
WTF? Someone has to accept responsibility for this mess.
Is grub development falling apart because a random dev can publish commits without parenting?
Is Archlinux falling apart because there is no time to block an upstream bug, that will break several systems? It’s not about a WM, or a DE, that we can live without, or with alternatives.