Legality vs morality, the problem is as old as the humanity. Legally they can perfectly use a sound alike, morally it's a shit move to ask the actress who voiced a very similar product, get a "no" and still decide to find a sound alike voice actress. If it was a non profit health care company you can be sure people would be much less outraged, but silicon valley's tech companies burned the little trust people had in them a long time ago, it's hard to have empathy for sociopath
Legally it becomes a problem if it can be shown that the intent was to copy the voice. In this case, it seems like Sam made that pretty clear with only a few bits of public info. If a case was brought against them I can only assume discovery would find internal emails or chats that spell out they were absolutely trying to replicate Scarlett Johansson's voice after she turned down their offer.
