Ok, running update-manager --debug shows me that:
INFO:root:holding back phased update grub-common (60 < 72) INFO:root:holding back phased update grub-efi-amd64-bin (60 < 72) INFO:root:holding back phased update grub-pc (60 < 72) INFO:root:holding back phased update grub-pc-bin (60 < 72) INFO:root:holding back phased update grub2-common (60 < 72)
So this is very confusing output in the case of a phased update involving two different source packages.
Ok, running update-manager --debug shows me that:
INFO:root:holding back phased update grub-common (60 < 72)
INFO:root:holding back phased update grub-efi-amd64-bin (60 < 72)
INFO:root:holding back phased update grub-pc (60 < 72)
INFO:root:holding back phased update grub-pc-bin (60 < 72)
INFO:root:holding back phased update grub2-common (60 < 72)
So this is very confusing output in the case of a phased update involving two different source packages.