I think the term is used in different ways.
I think it's useful sometimes to think of categories of garment as a capsule, i.e. my coat capsule -- do I have a coat for every weather I regularly encounter? Or do I need to update/ upgrade my puffer coat? Etc.
For certain people with specific lifestyle needs, thinking in terms of capsules by activity can also be helpful -- i.e. my hiking capsule, my skiing capsule, or even, my beach vacation capsule. (I have a hiking capsule that has only minimal crossover to daily or even other gear wear.)
Or you might think in terms of a PJ capsule or underwear capsule. I do, because I tend to upgrade these at intervals only. I examine them, see that I have my needs met, pay attention to what's falling apart and needs replacement.
Anyone who wears a lot of separates probably wants to think about mix and match, which is what those early magazine examples seem to be illustrating. Is that a capsule? Maybe it you buy all the parts at once? I don't know.
I don't like it when people congratulate themselves on their (supposedly, but not really) tiny "capsule" wardrobe (that they buy in its entirety every year.) That often feels self-congratulatory and smug to me. I think, yeah, of course everything goes together and mixes and matches perfectly and looks completely contemporary. -- you just bought an entire closet full of clothes at one time!
Note: I don't see anyone on this forum using the term in the latter way.