A patch for this issue has now been submitted in: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=967918
A new report was created since we ultimately propose to fix this in partman-efi instead of partman-auto.
A patch for this issue has now been submitted in: https://bugs.debian.org/cgi-bin/bugreport.cgi?bug=967918
A new report was created since we ultimately propose to fix this in partman-efi instead of partman-auto.