As an engineer, I can explain the possible causea of the wobbling. I do not have a PS4, so these are just guesses.
When you make large pastic parts, it will warp, meaning, that it create a slight curve & not straight. This effect can be reduce, but hard to eliminated. The latter is actually not need, for the very fact that the surface the unit may be placed on may not be full flat anyway.
Other possible explanation, is internal stress. When you need to screw things together, for instance, unless the screw surface perfectly in line, will have deformation, as the screw force the surface to match. This effect is worse when you have parts that are of different material, Classically metal with plastic, even one type of plastic to another, due to different sinkage/expension due to heat. Talking about heat, if PS4 is as overheating as mention, the wobbling will get worst!
Having said all that, unless the curving is massive, the simple solution is to have rubber stopper at the bottom of the console, not unlike the ones people put for chairs & table, & anything with 4 legs. I will be surprise if they do not have these, just to save on a few cents.
As an engineer, I would be ashame to tell people that my design wobble as bad as the gif picture, if true. These is the type of quality you expect from Chinese knock off electronics.
Having said all these, its not a deal breaker for me to get a console. Even if you happen to live in area where vibrations are common, you can just buy some more rubber to put under, & call it a day. Its certainly an engineering joke, but not a deal breaker, & you can be sure they will fix this in new batch, probably with bigger rubbers.
