> Had the developers stopped to plan they would have built something with over 16 bits of primary key

While true, this was in the 16-bit, Windows 1.x era. Also the ~640kb of RAM era (disks also werent that big either, DOS (v3.x) around that time only supported 32 MB partitions). Not sure which version of DOS Windows 1.0 ran on, I didnt use windows until v3.11 for Workgroups. A 32-bit primary key would likely have been seen as wasteful (not that I'm excusing it) and impractical, because you could likely never practically store more than 64k records on a PC of the day (and even if you could, you wouldnt have an disk left to do anything else).