On a technical level, your client is aware of everything in your own "inventory" at all times (meaning it is aware of bags, equipped, bank, shared, encumbered, etc even if you don't have them open or are near them). For other players the only populated storage is their current equipped items. As far as I'm aware this has always been the case. Though yes, the only way anyone would be able to read out another player's bank would be externally to the game like a public profile on efficiency or somehow getting hold of an API key they created.