The other thing that needs to be fixed here is that partman-auto needs to ensure that there is at least one primary partition. In other words, if there is already a primary partition on the disk, then it can happily make all the new ones logical; but if the disk is empty or there are only logical partitions, then it needs to make (an arbitrary) one of the new partitions primary or else it's possible that the BIOS will get upset later.
The other thing that needs to be fixed here is that partman-auto needs to ensure that there is at least one primary partition. In other words, if there is already a primary partition on the disk, then it can happily make all the new ones logical; but if the disk is empty or there are only logical partitions, then it needs to make (an arbitrary) one of the new partitions primary or else it's possible that the BIOS will get upset later.