A long time ago now, but I vaguely recall that the original PalmPilot OS chose to replicate the mistakes of the original Mac. Data structures exposed all over the place, apps had to implement the basics of event handling rather than have most of it handled for them.
I'm not sure what services PalmOS provided to the apps, but to my limited knowledge the apps themselves were non-multitasking, and had a standardized database per each app instead of the filesystem (i.e. something like proto-IndexedDB, but more oriented to documents or blobs). So it's kinda difficult to imagine them having the problems of quasi-multitasking and more complex MacOS. But perhaps things became involved by PalmOS 5.
Though the event handling part sounds like DOS' raw approach, versus Win95's abstraction—and I guess could plague any kind of a system.
