You need to patch debootstrap on host with this: https://salsa.debian.org/installer-team/debootstrap/-/merge_requests/92
The easiest way would probably be to run image-builder inside a PureOS container, as its debootstrap is already patched there.
(that’s a recent requirement since PureOS archive has been migrated to a newer infrastructure this week and the new version of laniakea got rid of some legacy stuff - but it turned out that while apt has supported that for ages, debootstrap still did not)