The closing part of 14.17.2 says:
Note that if the second partition's type is chosen
^^^^^^
appropriately, it is possible to have OpenBSD access both
partitions on the device. So, a Windows user could populate the
FAT32 partition with MP3 files which could be played when they
booted from the OpenBSD partition. I believe that calling it "the other partition" would be better wording, especially in the context of emphasizing how some other OS's might need their partition to be the _first_.

