In terms of overall learning/appreciation-of-how-things-work, I think it is important to understand that a program provided as an sfs (squashed filesystem) is not the same thing as a 'portable application'. An sfs version of a program may in fact NOT contain everything required to get that program to run; other parts of the program (some libs, for example) may still be expected to be provided by the underlying system. The term 'portable' is somewhat imprecise in that some so-called portable apps, provided in sfs form, may work on all or most recent Puppy systems, but perhaps not on other Linux distros (or on very old Pups) - i.e. it was designed specially for Puppy with knowledge of what most Puppy systems provide by default.
More general purpose 'portable apps' such as flatpack or snap packages or Appimages, tend to be much larger in size since they really do contain pretty much everything needed to get a package running so work pretty much on any distro capable of installing them - they also tend to be regularly updated to contain the latest versions of both the app and all its dependencies and so on. Disadvantage is that they therefore contain far more internally than a Puppy-destined-only 'portable sfs app' really requires, and again, there will always be trouble getting any modern app to also run on very old Linux systems.
An sfs can contain anything a person wants to add to a system (via the layering mechanism) - even just a single config file, for example. I can imagine it is quite difficult to make a Puppy portable app sfs file that works with recent Pups and also old Pups - one limiting factor is the age of the glibc on older Pups - whilst an sfs could be created to replace such major system components there is the problem of getting the new sfs to appear in higher layer (in order to overwrite the older libs) and also the issue that symlinks also sometimes need to be renamed such that other older apps still continue to work. Generally, however, these Pup-grown sfs apps are a great idea and very flexible and have been cleverly crafted to work on a wide range of Puppy systems.
