> If it weren't for their attempt to link the voice to SJ (i.e. with the "her" tweet), would that be OK?
No.
The fact that it sounds very much like her and it is for a virtual assistant that clearly draws a parallel to the virtual assistant voiced by SJ in the movie (and it was not a protected use like parody) makes it not OK and not legal.
> Surely it's OK to hire an English actor who sounds a lot like him, so long as I don't use Sir Patrick's name in the advertising.
Nope.
If you made it sound identical to Patrick Stewart that would also likely not be OK or legal since his voice and mannerisms are very distinctive.
If you made it sound kind of like Patrick Stewart that is where things get really grey and it is probably allowed (but if you're doing other things to draw parallels to Patrick Stewart / Star Trek / Picard then that'd make your case worse).
And the law deals with grey areas all the time. You can drag experts in voice and language into the court to testify as to how similar or dissimilar the two voices and mannerisms are. It doesn't nullify the law that there's a grey area that needs to get litigated over.
The things that make this case a slam dunk are that there's the relevant movie, plus there's the previous contact to SJ, plus there's the tweet with "Her" and supporting tweets clearly conflating the two together. You don't even really need the expert witnesses in this case because the behavior was so blatant.
And remember that you're not asking a computer program to analyze two recordings and determine similarity or dissimilarity in isolation. You're asking a judge to determine if someone was ripping off someone else's likeness for commercial purposes, and that judge will absolutely use everything they've learned about human behavior in their lifetime to weigh what they think was actually going on, including all the surrounding human context to the two voices in question.