Implications:

Illustration 8 - A new cylinder with Cylindrical, Spherical, Cube and Planar projected UVMaps in x,y,z and, in the case of the Cube, overlapping all, overlapping facing and no overlapping UVs.  Each row of three Projection orientations is flanked by a symbol of its map style.  The choice is clear here - USE FLAT PROJECTION MAPS. :)

What are the Implications here?

1. Choosing the correct Projection for your UVMap is a critical decision.  It can not be ignored or downplayed.  Often, even in tutorials, I have heard the authors base their choices on whatever the most convenient Projection is to produce a decent looking UVMap to start with.  As we can see in Illustration 5, the actual appearance of the UVMap does not matter as far as these ripping artifacts are concerned.  You could have the most beautiful UVMap or a UV-Trainwreck and it wouldn't affect a change in these artifacts.  (In THIS experiment.)  Choosing the Proper projection for your UVMap is critical if you wish to avoid these ripping artifacts..  After all, once you have selected that choice any further work is going to be wasted if you decide to change it and have been tweaking UVs by hand. 

2. Flat mapping, in my opinion, is always desired wherever possible as being the least likely to produce ripping artifacts. I've always preferred to use them and, now that I think on it, the ONLY times I have encountered ripping artifacts was when I did not use a flat projection.  However, that's not saying much as I don't model inorganics very often (strict box/cylinder/sphere/linear-symmetrica-type shapes) and am in the habit of using planar maps already.

3)  Because of the many choices available, there were some experiments I haven't done yet.  In particular, the choice of shading regions/material zones and their borders, multiple-mapped objects, widely different shapes, bad UVmaps for all projections, etc..  The permutations of possibilities with multiple projection choices and almost infinite variety of objects is endless.  So, this is not definitive by any means and should only be considered experimentally validated for the experimental object investigated - The simple cylinder.  It also doesn't take into account someone's tenacity and tweaking, prodding, pulling and distorting a UVMap - It's possible they could "correct" the issue by some random spaghettifying of their improperly projected UVMap.  I dunno... Investigating that takes too much work and I'm allergic to that...

4. Lastly, and most importantly, choosing the proper Projection will sometimes be a matter of experience.  Consider that in Illustration 8, we have what one would think is an obvious choice - Just slap a cylinder map on it.  But, only one projected along the y-axis gives any desirable results.  Even then, that's only good for a fast map that you're not really worried about putting an image on.  If you're going to put an image on it, manipulating that particular projection style wouldn't be as easy as others.  But, if we really want the sides of the cylinder to be easy to manipulate, we may be tempted to choose a z-axis or x-axis projection.  As we can see, those would be bad choices.

In all cases, across all tests, the Flat Projection method yielded results without artifacts 100% of the time.  The best any other method provided, with this object, was a 30% success rate.  Does this apply to other models as well?  As far as the ripping artifact is concerned, I believe we can say with some confidence that it would.  Certainly, I think we can conclude that choosing an improper Projection map for an object could have similar results and ripping artifacts could occur.

I leave the rest to the reader to decide.  There are those much more knowledgeable than I with professional experience and training that may have technical knowledge that would be valuable here.  I am only a hobbyist intrigued by a troublesome question and have attempted to provide an answer for it as best I can with the knowledge I have gathered so far.

I'll continue investigating this type of artifact in other objects, other maps and across as wide a spectrum as possible of common uses for Poser and the topic of modeling for Poser.