Accumulating stuff that "might be useful" at some indefinite point in the future, without trying to curate the accumulation might not be hoarding, but, it's actually quite similar to the mindset of some of the actual hoarders on the TV show Hoarders. Those people obviously take it to pathological extremes, and I'm not suggesting having a bunch of empty, cleaned out yogurt containers stashed away somewhere is in any way equivalent to stuffing one's entire house from floor to ceiling with stuff. But, on the show, when the hoarders talk about why they do it, it's often a behavior that came about as a reaction to some kind of loss, or out of a fear of some kind of loss. I would suggest that what you've described ("I'll hold on to this 'just in case....") is a lot like the reasons they give for doing it, even if the real motivation is quite different.

There are differences as well. Magnitude is the obvious one, unless you actually filled your entire kitchen with yogurt containers or something lol. :) The other big one I can think of is that an actual hoarder will have genuine, severe anxiety at the mere thought of getting rid of anything from their hoard. This is another assumption, of course, but my guess is that if you had to get rid of some, or maybe even most of your accumulation of yogurt containers for some reason, you'd be able to do that, and the thought wouldn't fill you with dread or anything.