I know nothing about the mathematics. But I think it's fair to say that in general people tend think of particles as being a _stable_ unit of some sort. So the

I know nothing about the mathematics. But I think it's fair to say that in general people tend think of particles as being a _stable_ unit of some sort. So the term "particle" becomes less appropriate the less stable something is, and time is often a factor when thinking about stability. If someone were simply to slam 4 neutrons together, for how long would they need to stay together for this to be deemed a real particle? I think it's for this reason the original commenter quoted the use of the term "particle".