Seems like so, yes.
Devs did say why they made the Plundra mirror itself in all safehouses. It is for quality of life since with 100 safehouses on the map, try to remember into which Plundra you put one specific item that you need if each Plundra would have it’s independent storage. So, to avoid that frustration, all Plundras share their storage.
The first part of your sentence is contradictory to what you just said. Right now, we have 200 unit storage in Plundra, regardless which safehouse you’re in. If each Plundra would have it’s independent storage, then we’d have: 100 safehouses times 200 unit per Plundra = 200000 unit storage in the game.
The second part of your sentence was true in the early days since back then, there was no Plundra what-so-ever and you only had what you could carry. Also, your carry capacity was half of what it currently is. (Those were the good old days.) Plundra came to be in August '19 update.