I can vouch for this.
I reported a bug about shift+click buying the keys from vendors not working properly back shortly after the game was released… If a non-full key stack doesn’t exist in your personal inventory, it will buy the # the vendor has first, then you have to shift+click again to fill the stack… Instead of just buying a full stack the first time like it does in the OG.
It’s still not fixed.
I guess not enough people have complained about it yet. 