This does seem to be sound advice, and I appreciate everyone for pointing it out. I think the key is recognizing what level of compartmentalization is appropriate for a particular situation.

Public object methods are a widely recognized contract that, without warning well in advance, the effects of calling a method will not change. The safety of compartmentalizing comes from that contract alone, not the form of the compartment. If I take any space and give it the same contract, it becomes a compartment of just such strength. By doing so you make available compartments of different shapes and sizes, from a simple scalar to the most complicated data structure. The line of delineation is no longer what one might expect- until they read the documentation that details it.

It is the compartmentalization, not how you effect the compartmentalization, that makes it useful. Does it make sense to re-use common, publicly acknowledged contracts to do so? Yes (see Creative Commons). Is it wise to follow that as a guideline unless you have good reason to do otherwise? Sure. But might there be uses that don't follow the guidelines? I believe so. Hence, this entire thread.