kthreadd (1558445) writes "GNU GRUB has been updated to version 1.99. Among the many improvements are support for two new filesystems, BtrFS and ZFS. For Linux users this means that it's now possible to move to BtrFS entirely and not use it only for non-bootable volumes." Link to Original Source
If it happens once, it's a bug. If it happens twice, it's a feature.
If it happens more than twice, it's a design philosophy.