It's not a bug, it's intended behavior. The official release of ZFS on Linux I believe only supports kernel 5.x. Since arch is always on the cutting edge, the

It's not a bug, it's intended behavior. The official release of ZFS on Linux I believe only supports kernel 5.x. Since arch is always on the cutting edge, the repo maintainers need to manually test the driver with each new kernel release before pushing it out to the world. They stop you from borking your system in the interim by having a strict version requirement for Linux on the zfs package. Pacman only does that check, though, once the -Sy operation has finished