A lot of other players in the replies alone share the same sentiment. I hope an update will be rolled out as a hotfix rather than for the next patch update, 'cos I had to stop playing because of this feature. And I hope the solution isn't just simply removing the story item tag on character containers. At least add into the prompt about whether you want to have the dismissed companion their stuff or not, or have an option in the settings to disable the feature altogether.
Alternatively, just make the inventories of all characters be shared, at least when in camp. I have only played Pathfinder: Wrath of the Righteous - a 3.5e DnD system - and not familiar with the 5e (Baldur's Gate 3) system, though I hope the game was made to be tedious not because of that. In the meantime, I'm going to have to take a break from playing my 7th rerun and the game. I was in the Druid's Grove when I found out about this after updating my game, and I dismissed Lae'zel to recruit Wyll.
