I've discovered that, when using a "flat" layout, swap partitions are similarly misidentified as type 0x83 (on MBR) or 0FC63DAF-8483-4772-8E79-3D69D8477DE4 (on GPT), when they should be 0x82 (on MBR) or 0657FD6D-A4AB-43C4-84E5-0933C84B4F4F (on GPT; 8200 in gdisk).
I've discovered that, when using a "flat" layout, swap partitions are similarly misidentified as type 0x83 (on MBR) or 0FC63DAF- 8483-4772- 8E79-3D69D8477D E4 (on GPT), when they should be 0x82 (on MBR) or 0657FD6D- A4AB-43C4- 84E5-0933C84B4F 4F (on GPT; 8200 in gdisk).