No they are not about saying "hello". The hadith explicitly mention saying salaam.
It doesn't matter if the kafir is not a jew or a chirstian. The fact that the rest of the kuffar are worse in their disbelief than jews or christians, the prohibition to send salaam to them only becomes stronger. The logic is easy to spot.
The hadith is simple, to the point, for all times and supposed to be taken literally!
Here are some contradictions about your approach to interpretation, sharaabi.
saying salam was likely the customary way to greet anyone in arabia even before islam. so this is the equivalent of a hello in today's context.
salaam is explicitly mentioned, and so are jews and christians. not the idolaters. but you'd like to use logic to extend the prohibition to other disbelievers as well, but not extend the greeting to other equivalent forms.
and you end with a claim of necessity for the hadeeth to be taken literally. what happened to previous ideas of logic and context?
either leave the liberty of logic to all parts of scripture (like zobia's interpretation), or take everything literally. don't pick and choose to match your current prejudices.